Nonaqueous electrolyte, capacitor device using same, and carboxylic acid ester compound used in same

ABSTRACT

The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I).In the formula, each of R1 and R2 independently represents a hydrogen atom, a —C(═O)—OR4 group, or the like, and R1 and R2 may be bonded to each other to form a ring structure. R3 represents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and R4 represent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O)2— group, an —S(═O)2—R5—S(═O)2— group or a CR6R7 group, R5 represents an alkylene group having 1 to 4 carbon atoms, and each of R6 and R7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

TECHNICAL FIELD

The present invention relates to a nonaqueous electrolytic solutioncapable of improving electrochemical characteristics in using an energystorage device at a high voltage, an energy storage device using thesame, and a carboxylic acid ester compound to be used for the same.

BACKGROUND ART

An energy storage device, especially a lithium secondary battery, hasbeen widely used recently for a power source of a small-sized electronicdevice, such as a mobile telephone, a notebook personal computer, etc.,and a power source for an electric vehicle or electric power storage.With respect to a thin electronic device, such as a tablet device, anultrabook, etc., a laminate-type battery or a prismatic battery using alaminate film, such as an aluminum laminate film, etc., for an outerpackaging member thereof is frequently used. In such a battery, theouter packaging member is thin, and therefore, there is involved such aproblem that the battery is easily deformed even by a bit of expansionof the outer packaging member and the deformation very likely influencesthe electronic device.

A lithium secondary battery is mainly constituted of a positiveelectrode and a negative electrode, each containing a material capableof absorbing and releasing lithium, and a nonaqueous electrolyticsolution including a lithium salt and a nonaqueous solvent; and acarbonate, such as ethylene carbonate (EC), propylene carbonate (PC),etc., is used as the nonaqueous solvent.

In addition, a lithium metal, a metal compound capable of absorbing andreleasing lithium (e.g., a metal elemental substance, a metal oxide, analloy with lithium, etc.), and a carbon material are known as thenegative electrode of the lithium secondary battery. In particular, anonaqueous electrolytic solution secondary battery using, as the carbonmaterial, a carbon material capable of absorbing and releasing lithium,for example, coke or graphite (e.g., artificial graphite or naturalgraphite), etc., is widely put into practical use.

Since the aforementioned negative electrode material stores and releaseslithium and an electron at an extremely electronegative potential equalto the lithium metal, it has a possibility that a lot of solvents aresubjected to reductive decomposition, and a part of the solvent in theelectrolytic solution is reductively decomposed on the negativeelectrode regardless of the kind of the negative electrode material, sothat there were involved such problems that the movement of a lithiumion is disturbed due to deposition of decomposed products, generation ofa gas, or expansion of the electrode, thereby worsening batterycharacteristics, such as cycle properties, etc., especially in the caseof using the battery at a high temperature and at a high voltage; andthat the battery is deformed due to expansion of the electrode.Furthermore, it is known that a lithium secondary battery using alithium metal or an alloy thereof, a metal elemental substance, such astin, silicon, etc., or a metal oxide thereof as the negative electrodematerial may have a high initial battery capacity, but the batterycapacity and the battery performance thereof, such as cycle properties,may be largely worsened because the micronized powdering of the materialmay be promoted during cycles, which brings about accelerated reductivedecomposition of the nonaqueous solvent, as compared with the negativeelectrode formed of a carbon material, and the battery may be deformeddue to expansion of the electrode.

Meanwhile, since a material capable of absorbing and releasing lithium,which is used as a positive electrode material, such as LiCoO₂, LiMn₂O₄,LiNiO₂, LiFePO₄, etc., stores and releases lithium and an electron at anelectropositive voltage of 3.5 V or more on the lithium basis, it has apossibility that a lot of solvents are subjected to oxidativedecomposition especially in the case of using the battery at a hightemperature and at a high voltage, and a part of the solvent in theelectrolytic solution is oxidatively decomposed on the positiveelectrode regardless of the kind of the positive electrode material, sothat there were involved such problems that the resistance is increaseddue to deposition of decomposed products; and that a gas is generateddue to decomposition of the solvent, thereby expanding the battery.

Under such a situation, in electronic devices having a lithium secondarybattery mounted therein, the electric power consumption increases, andthe capacity increases steadily. The electrolytic solution is in theenvironment where the decomposition is apt to take place more and moredue to an increase of temperature of the battery by the heat generationfrom the electronic device, an increase of voltage of charging settingvoltage of the battery, and the like. Thus, there was involved such aproblem that the battery becomes unable to be used due to expansion ofthe battery caused by the gas generation, actuation of a safetymechanism to cut off the current, etc., or the like.

Irrespective of the foregoing situation, the multifunctionality ofelectronic devices on which lithium secondary batteries are mounted ismore and more advanced, and the electric power consumption tends toincrease. The capacity of the lithium secondary battery is thus beingmuch increased, and because of an increase of a density of the battery,a reduction of a useless space capacity within the battery, and so on, avolume occupied by the nonaqueous electrolytic solution in the batteryis becoming small. In consequence, it is the present situation that inthe case of using the battery at a high temperature and at a highvoltage, the battery performance is apt to be worsened by decompositionof a bit of the nonaqueous electrolytic solution.

PTL 1 discloses dihydro-furo[3,4-d]-1,3-dioxole-2,4,6-trione as one ofbicyclo compounds and suggests that when added to an electrolyticsolution, the electrochemical characteristics of the battery, especiallythe cycle capacity retention rate at 55° C., is improved.

PTL 2 discloses diethyl 2-oxo-1,3-dioxolane-4,5-dicarboxylate havingtetraethylammonium tetrafluoroborate dissolved therein as anelectrolytic solution.

PTL 3 suggests that when an electrolytic solution containingmethacryloxymethyl ethylene carbonate is used, even in the case of usinghigh-crystalline carbon for a negative electrode, the reductivedecomposition of the solvent is inhibited, and the charging anddischarging efficiency is improved.

PTL 4 proposes a nonaqueous electrolytic solution containing a cyclicsulfuric acid ester, such as an ethylene glycol sulfuric acid ester,etc., and describes that the decomposition and deterioration of theelectrolytic solution on the electrode surface are inhibited.

PTL 5 proposes a nonaqueous electrolytic solution containing ethylenesulfite and vinylene carbonate and describes that the 25° C. cyclecharacteristics are improved.

PTL 6 proposes a nonaqueous electrolytic solution containing a cyclicether compound, such as 1,3-dioxane, 1,3-dioxolane, etc., and describesthat a reaction of a positive electrode with the electrolytic solutionat a high temperature is inhibited, so that the safety is improved.

PTL 7 proposes a nonaqueous electrolytic solution containing1,5,2,4-dioxadithiepane 2,2,4,4-tetraoxide and suggests that the cyclecharacteristics and storage characteristics are improved.

PTL 1: US 2012/0088160A

PTL 2: JP-A 7-285960

PTL 3: JP-A 2000-40526

PTL 4: JP-A 10-189042

PTL 5: JP-A 11-121032

PTL 6: JP-A 2014-72050

PTL 7: JP-A 2004-281368

DISCLOSURE OF INVENTION Technical Problem

Problems to be solved by the present invention are to provide anonaqueous electrolytic solution capable of improving electrochemicalcharacteristics in the case of using an energy storage device at a hightemperature and at a high voltage and further capable of inhibiting thegas generation as well as improving a capacity retention rate afterstorage at a high voltage and at a high temperature, and also to providean energy storage device using the same and a carboxylic acid estercompound to be used for the same.

Solution to Problem

The present inventors made extensive and intensive investigationsregarding the performance of the nonaqueous electrolytic solutions ofthe aforementioned conventional technologies. As a result, according tothe nonaqueous electrolyte secondary batteries of PTLs 1 and 3, in fact,the effect could not be substantially exhibited against the problem ofinhibiting the gas generation following charging and discharging in thecase of using an energy storage device at a high temperature and at ahigh voltage.

According to the nonaqueous electrolyte secondary batteries of PTLs 4and 5, in fact, the effect could not be substantially exhibited againstthe problem of inhibiting the gas generation following charging anddischarging in the case of using an energy storage device at a hightemperature and at a high voltage. In addition, according to the cyclicether compound described in PTL 6, though it was perceived to make thegas generation gentle, its effect was insufficient.

Even according to the nonaqueous electrolyte secondary battery of PTL 7,in fact, the effect could not be substantially exhibited against theproblem of inhibiting the gas generation following charging anddischarging in the case of using an energy storage device at a hightemperature and at a high voltage.

Then, in order to solve the foregoing problems, the present inventorsmade extensive and intensive investigations. As a result, it has beenfound that by adding a specified carboxylic acid ester compound, thecapacity retention rate after storage in the case of using an energystorage device at a high temperature and at a high voltage can beimproved, and also, the gas generation can be inhibited, leading toaccomplishment of the present invention.

Specifically, the present invention provides the following (1) to (4).

(1) A nonaqueous electrolytic solution having an electrolyte saltdissolved in a nonaqueous solvent, the nonaqueous electrolytic solutioncontaining a carboxylic acid ester compound represented by the followinggeneral formula (I).

In the formula, each of R¹ and R² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, an aryl group having 6 to 12carbon atoms, or a —C(═O)—OR⁴ group, and when R¹ and R² are each analkyl group, then R¹ and R² may be bonded to each other to form a ringstructure. R³ represents a hydrogen atom, a halogen atom, or an alkylgroup having 1 to 6 carbon atoms, and n represents an integer of 1 to 3.

When n is 1, then L and R⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, or anaryl group having 6 to 12 carbon atoms, and when n is 2 or 3, then Lrepresents an n-valent connecting group constituted of a carbon atom anda hydrogen atom, which may contain an ether bond, a thioether bond, oran SO₂ bond, and R⁴ is the same as described above.

X represents a —C(═O)— group, an —S(═O)— group, an —S(═O)₂— group, an—S(═O)₂—R⁵—S(═O)₂— group or a CR⁶R⁷ group, R⁵ represents an alkylenegroup having 1 to 4 carbon atoms, in which at least one hydrogen atommay be substituted with a halogen group or an alkyl group having 1 to 4carbon atoms, and each of R⁶ and R⁷ independently represents a hydrogenatom or an alkyl group having 1 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom.

At least one hydrogen atom of the alkyl group having 1 to 6 carbonatoms, the cycloalkyl group having 3 to 6 carbon atoms, the alkenylgroup having 2 to 6 carbon atoms, the alkynyl group having 3 to 6 carbonatoms, the alkoxyalkyl group having 2 to 6 carbon atoms, the cyanoalkylgroup having 2 to 6 carbon atoms, the aralkyl group having 7 to 13carbon atoms, or the aryl group having 6 to 12 carbon atoms as R¹, R²,R⁴, or L, may be substituted with a halogen atom.

(2) An energy storage device including a positive electrode, a negativeelectrode, and a nonaqueous electrolytic solution having an electrolytesalt dissolved in a nonaqueous solvent, the nonaqueous electrolyticsolution being the nonaqueous electrolytic solution as set forth abovein (1).(3) A carboxylic acid ester compound represented by the followinggeneral formula (II).

In the formula, each of R⁴¹ and R⁴² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR⁴⁴ group, and when R⁴¹and R⁴² are each an alkyl group, then R⁴¹ and R⁴² may be bonded to eachother to form a ring structure. R⁴³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and mrepresents 1 or 2.

When m is 1, then L⁴ and R⁴⁴ may be the same as or different from eachother and represent a halogenated alkyl group having 1 to 6 carbonatoms, in which at least one hydrogen atom is substituted with a halogenatom, a halogenated cycloalkyl group having 3 to 6 carbon atoms, inwhich at least one hydrogen atom is substituted with a halogen atom, analkenyl group having 2 to 6 carbon atoms, in which at least one hydrogenatom may be substituted with a halogen atom, an alkynyl group having 3to 6 carbon atoms, an alkoxyalkyl group having 3 to 6 carbon atoms, acyanoalkyl group having 2 to 6 carbon atoms, a halogenated aralkyl grouphaving 7 to 13 carbon atoms, in which at least one hydrogen atom issubstituted with a halogen atom, or a halogenated aryl group having 6 to12 carbon atoms, in which at least one hydrogen atom is substituted witha halogen atom, and when m is 2, then L⁴ represents an alkylene grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom issubstituted with a halogen atom, an alkenylene group having 4 to 8carbon atoms, or an alkynylene group having 4 to 8 carbon atoms and R¹⁴is the same as described above, provided that when m is 1, then L⁴ isnot a 3-methyl-2-buten-1-yl group.

(4) A carboxylic acid ester compound represented by the followinggeneral formula (III).

In the formula, each of R⁵¹ and R⁵² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, an aryl group having 6 to 12carbon atoms, or a —C(═O)—OR⁴ group, and when R⁵¹ and R⁵² are each analkyl group, then R⁵¹ and R⁵² may be bonded to each other to form a ringstructure. R⁵³ represents a hydrogen atom, a halogen atom, or an alkylgroup having 1 to 6 carbon atoms, and m represents 1 or 2.

When m is 1, then L⁵ and R⁵⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, or anaryl group having 6 to 12 carbon atoms, and when m is 2, then ULrepresents an alkylene group having 2 to 8 carbon atoms, an alkenylenegroup having 4 to 8 carbon atoms, or an alkynylene group having 4 to 8carbon atoms, at least one hydrogen atom of L⁵ may be substituted with ahalogen atom, and R⁵⁴ is the same as described above.

X³ represents an —S(═O)₂—R⁵⁵—S(═O)₂— group, and R⁵⁵ represents analkylene group having 1 to 4 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom or an alkyl grouphaving 1 to 4 carbon atoms.

At least one hydrogen atom of the alkyl group having 1 to 6 carbonatoms, the cycloalkyl group having 3 to 6 carbon atoms, the alkenylgroup having 2 to 6 carbon atoms, the alkynyl group having 3 to 6 carbonatoms, the alkoxyalkyl group having 2 to 6 carbon atoms, the cyanoalkylgroup having 2 to 6 carbon atoms, the aralkyl group having 7 to 13carbon atoms, or the aryl group having 6 to 12 carbon atoms as R⁵¹, R⁵²,R⁵⁴, or L⁵, may be substituted with a halogen atom.

Advantageous Effects of Invention

According to the present invention, it is possible to provide anonaqueous electrolytic solution capable of not only improving acapacity retention rate after storage but also inhibiting the gasgeneration in the case of using an energy storage device at a hightemperature and at a high voltage, and also to provide an energy storagedevice, such as a lithium battery, etc., using the same and a carboxylicacid ester compound to be used for the same.

DESCRIPTION OF EMBODIMENTS

The nonaqueous electrolytic solution of the present invention isconcerned with a nonaqueous electrolytic solution having an electrolytesalt dissolved in a nonaqueous solvent, the nonaqueous electrolyticsolution containing a carboxylic acid ester compound represented by thefollowing general formula (I).

In the formula R¹, R², R³, X, L, and n are the same as described above.

In the nonaqueous electrolytic solution of the present invention, acontent of the carboxylic acid ester compound represented by theforegoing general formula (I) is preferably 0.001% by mass or more, morepreferably 0.01% by mass or more, and still more preferably 0.3% by massor more, and preferably 30% by mass or less, more preferably 20% by massor less, still more preferably 10% by mass or less, and yet still morepreferably 5% by mass or less from the viewpoint of forming anappropriate surface film on an electrode, thereby enhancing an improvingeffect of storage characteristics in the case of using a battery at ahigh temperature and at a high voltage.

The nonaqueous electrolytic solution of the present invention preferablyincludes the following three embodiments.

Embodiment 1

Embodiment 1 is an embodiment of using, as the carboxylic acid estercompound represented by the foregoing general formula (I), a compoundwherein X is a —C(═O)— group, and n is an integer of 1 to 3.

More specifically, the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent is a nonaqueouselectrolytic solution containing a carboxylic acid ester compoundrepresented by the following general formula (I-1).

In the formula, each of R¹¹ and R¹² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR¹⁴ group, and when R¹¹and R¹² are each an alkyl group, then R¹¹ and R¹² may be bonded to eachother to form a ring structure. R¹³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and nrepresents an integer of 1 to 3.

When n is 1, then L and R¹⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, in whichat least one hydrogen atom may be substituted with a halogen atom, acycloalkyl group having 3 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an alkenyl grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkynyl group having 3 to 6 carbonatoms, an alkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkylgroup having 2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, or an aryl group having 6 to 12 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, and whenn is 2 or 3, then L represents an n-valent connecting group constitutedof a carbon atom and a hydrogen atom, which may contain an ether bond, athioether bond, or an SO₂ bond, at least one hydrogen atom of L may besubstituted with a halogen atom, and R¹⁴ is the same as described above.

Embodiment 21

Embodiment 2 is an embodiment of using, as the carboxylic acid estercompound represented by the foregoing general formula (I), a compoundwherein X is an —S(═O)— group, an —S(═O)₂— group, or a —CR⁶R⁷ group, andn is 1.

More specifically, the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent is a nonaqueouselectrolytic solution containing a carboxylic acid ester compoundrepresented by the following general formula (I-2).

In the formula, each of R²¹ and R²² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR²⁵ group, and when R²¹and R²² are each an alkyl group, then R²¹ and R²² may be bonded to eachother to form a ring structure. R²³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and R²⁴ andR²⁵ may be the same as or different from each other and represent analkyl group having 1 to 6 carbon atoms, in which at least one hydrogenatom may be substituted with a halogen atom, a cycloalkyl group having 3to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkenyl group having 2 to 6 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,or an aryl group having 6 to 12 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom. X¹ represents an—S(═O) group, an —S(═O)₂ group, or a —CR²⁶R²⁷ group and each of R²⁶ andR²⁷ independently represents a hydrogen atom or an alkyl group having 1to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom.

Embodiment 3

Embodiment 3 is an embodiment of using, as the carboxylic acid estercompound represented by the foregoing general formula (I), a compoundwherein X is an —S(═O)₂—R⁵—S(═O)₂— group, and n is 1 or 2.

More specifically, the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent is a nonaqueouselectrolytic solution containing a carboxylic acid ester compoundrepresented by the following general formula (I-3).

In the formula, each of R³¹ and R³² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,an aryl group having 6 to 12 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, or a —C(═O)—OR³⁴group. R³³ represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 6 carbon atoms, and m represents 1 or 2.

When m is 1, then L³ and R³⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, in whichat least one hydrogen atom may be substituted with a halogen atom, acycloalkyl group having 3 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an alkenyl grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkynyl group having 3 to 6 carbonatoms, an alkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkylgroup having 2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, or an aryl group having 6 to 12 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, and whenm is 2, then L^(a) represents an alkylene group having 2 to 8 carbonatoms, an alkenylene group having 4 to 8 carbon atoms, or an alkynylenegroup having 4 to 8 carbon atoms, at least one hydrogen atom of L³ maybe substituted with a halogen atom, and R³⁴ is the same as describedabove.

X² represents an —S(═O)₂—R³—S(═O)₂— group, and R³⁵ represents analkylene group having 1 to 4 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom or an alkyl grouphaving 1 to 4 carbon atoms.

[Nonaqueous Electrolytic Solution of Embodiment 1]

According to the nonaqueous electrolytic solution of Embodiment 1 of thepresent invention, in the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent, the compoundrepresented by the foregoing general formula (I) wherein X is a —C(═O)—group, and n is an integer of 1 to 3, more specifically the carboxylicacid ester compound represented by the foregoing general formula (I-1)is contained in the nonaqueous electrolytic solution.

Although the reasons why the nonaqueous electrolytic solution ofEmbodiment 1 is able to greatly improve the electrochemicalcharacteristics of an energy storage device when used at a hightemperature and at a high voltage are not always elucidated yet, thefollowing may be considered.

In view of the fact that the compound represented by the general formula(I-1), which is used in Embodiment 1, has a hetero ring which isreductively decomposed at the α-position of the carbonyl group to form asurface film, it has high reactivity and quickly reacts with activesites of both a positive electrode and a negative electrode, therebyforming a firmer surface film. Therefore, it may be considered that notonly the storage characteristics at a high temperature and at a highvoltage are improved, but also the gas generation to be caused due todecomposition of the solvent is inhibited.

The carboxylic acid ester compound which is contained in the nonaqueouselectrolytic solution of Embodiment 1 is represented by the followinggeneral formula (I-1).

In the formula, each of R¹¹ and R¹² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR¹⁴ group, and when R¹ andR^(1L) are each an alkyl group, then R¹¹ and R¹² may be bonded to eachother to form a ring structure. R¹³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and nrepresents an integer of 1 to 3.

When n is 1, then L and R¹⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, in whichat least one hydrogen atom may be substituted with a halogen atom, acycloalkyl group having 3 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an alkenyl grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkynyl group having 3 to 6 carbonatoms, an alkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkylgroup having 2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, or an aryl group having 6 to 12 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, and whenn is 2 or 3, then L represents an n-valent connecting group constitutedof a carbon atom and a hydrogen atom, which may contain an ether bond, athioether bond, or an SO₂ bond, at least one hydrogen atom of L may besubstituted with a halogen atom, and R¹⁴ is the same as described above.

In the foregoing general formula (I-1), each of R¹¹ and R¹² isindependently preferably a hydrogen atom, a halogen atom, an alkyl grouphaving 1 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, a cycloalkyl group having 3 to 6 carbonatoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl grouphaving 3 to 6 carbon atoms, or a —C(═O)—OR¹⁴ group, and more preferablya hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, or a —C(═O)—OR¹ group. When R¹¹ and R¹² are each an alkylgroup, then R¹¹ and R¹² may be bonded to each other to form a ringstructure.

R¹³ is preferably a hydrogen atom or a halogen atom, and more preferablya hydrogen atom. n is preferably 1 or 2, and more preferably 1.

When n is 1, then L and R¹⁴ may be the same as or different from eachother and are preferably an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an alkenyl grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkynyl group having 3 to 6 carbonatoms, or an aryl group having 6 to 12 carbon atoms, in which at leastone hydrogen atom may be substituted with a halogen atom, and morepreferably an alkenyl group having 2 to 6 carbon atoms or an alkynylgroup having 3 to 6 carbon atoms.

As specific examples of R¹¹ and R¹², there are suitably exemplified ahydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom,a bromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a 3-pentyl group,a tert-butyl group, a tert-amyl group, etc.; a halogenated alkyl group,such as a fluoromethyl group, a difluoromethyl group, a trifluoromethylgroup, a 2-chloroethyl group, a 2-fluoroethyl group, a 2,2-difluoroethylgroup, a 2,2,2-trifluoroethyl group, a 3-fluoropropyl group, a3-chloropropyl group, a 3,3-difluoropropyl group, a3,3,3-trifluoropropyl group, a 2,2,3,3-tetrafluoropropyl group, a2,2,3,3,3-pentafluoropropyl group, etc.; a cycloalkyl group, such as acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, etc.; an alkenyl group, such as vinyl group,a 1-propen-1-yl group, a 2-propen-1-yl group, a 2-buten-1-yl group, a3-buten-1-yl group, a 4-penten-1-yl group, a 5-hexen-1-yl group, a1-propen-2-yl group, a 1-buten-2-yl group, a 2-methyl-2-propen-1-ylgroup, etc.; an alkynyl group, such as an ethynyl group, a 2-propynylgroup, a 2-butynyl group, a 3-butynyl group, a 4-heptynyl group, a1-methyl-2-propynyl group, a 1,1-dimethyl-2-propynyl group, a1-methyl-3-butynyl group, a 1-methyl-4-heptynyl group, etc.; an aralkylgroup, such as a benzyl group, a 4-methylbenzyl group, a4-tert-butylbenzyl group, a 4-fluorobenzyl group, a 4-chlorobenzylgroup, a 1-phenylethan-1-yl group, a 2-phenylothan-1-yl group, a3-phenylpropan-1-yl group, etc.; and an aryl group, such as a phenylgroup, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenylgroup, a 4-tert-butylphenyl group, a 2-fluorophenyl group, a4-fluorophenyl group, a 2-trifluoromethylphenyl group, a3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a4-fluoro-2-trifluoromethylphenyl group, a4-fluoro-3-trifluoromethylphenyl group, a 2,6-difluorophenyl group, a3,5-difluorophenyl group, a 2,4,6-trifluorophenyl group, a2,3,5,6-tetrafluorophenyl group, a perfluorophenyl group, etc.; and alsoa methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a cyclopentyloxycarbonylgroup, a cyclohexyloxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, abenzyloxycarbonyl group, a phenyloxycarbonyl group, a4-fluorophenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonylgroup, a 4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, a perfluorophenyloxycarbonylgroup, and the like.

Of the foregoing, R¹¹ and R¹² are preferably a hydrogen atom, a fluorineatom, a chlorine atom, a methyl group, an ethyl group, an n-propylgroup, an n-butyl group, an n-pentyl group, an n-hexyl group, anisopropyl group, a sec-butyl group, a tert-butyl group, atrifluoromethyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a cyclopentyl group, a cyclohexylgroup, a vinyl group, a 1-propen-1-yl group, a 2-propen-1-yl group, a2-buten-1-yl group, a 1-propen-2-yl group, a 2-methyl-2-propen-1-ylgroup, an ethynyl group, a 2-propynyl group, a 1-methyl-2-propynylgroup, a methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, aphenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonyl group, a4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, or aperfluorophenyloxycarbonyl group; and more preferably a hydrogen atom, afluorine atom, a methyl group, an ethyl group, a trifluoromethyl group,a 2-propen-1-yloxycarbonyl group, or a 2-propenyloxycarbonyl group.

When R¹¹ and R¹² are each an alkyl group, then R¹¹ and R¹² may be bondedto each other to form a ring structure. As specific examples thereof,there are suitably exemplified an ethane-1,2-diyl group, apropane-1,3-diyl group, a butane-1,4-diyl group, and a pentane-1,5-diylgroup, with a butane-1,4-diyl group or a pentane-1,5-diyl group beingpreferred.

As specific examples of R¹³, there are suitably exemplified a hydrogenatom; a halogen atom, such as a fluorine atom, a chlorine atom, abromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; and a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a pentan-3-ylgroup, a tert-butyl group, a tert-amyl group, etc. Above all, a hydrogenatom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group,an n-propyl group, an n-butyl group, an isopropyl group, a sec-butylgroup, or a tert-butyl group is preferred, with a hydrogen atom, afluorine atom, a methyl group, or an ethyl group being more preferred.

As specific examples of L, there are suitably exemplified the followinggroups.

(i) In the case of n=1:

There are suitably exemplified a straight-chain alkyl group, such as amethyl group, an ethyl group, an n-propyl group, an n-butyl group, ann-pentyl group, an n-hexyl group, etc.; a branched alkyl group, such asan isopropyl group, a sec-butyl group, a 2-pentyl group, a 3-pentylgroup, a tert-butyl group, a tert-amyl group, etc.; a halogenated alkylgroup, such as a fluoromethyl group, a difluoromethyl group, a2-chloroethyl group, a 2-fluoroethyl group, a 2,2-difluoroethyl group, a2,2,2-trifluoroethyl group, a 3-fluoropropyl group, a 3-chloropropylgroup, a 3,3-difluoropropyl group, a 3,3,3-trifluoropropyl group, a2,2,3,3-tetrafluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group,etc.; a cycloalkyl group, such as a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group,etc.; a halogenated cycloalkyl group, such as a 4-fluorocyclohexylgroup, a 4-chlorocyclohexyl group, etc.; an alkenyl group, such as avinyl group, a 1-propen-1-yl group, a 2-propen-1-yl group, a2-buten-1-yl group, a 3-buten-1-yl group, a 4-penten-1-yl group, a5-hexen-1-yl group, a 1-propen-2-yl group, a 1-buten-2-yl group, a2-methyl-2-propen-1-yl group, etc.; a haloalkenyl group, such as a3,3-difluoro-2-propen-1-yl group, a 4,4-difluoro-3-buten-1-yl group, a3,3-dichloro-2-propen-1-yl group, a 4,4-dichloro-3-buten-1-yl group,etc.; an alkynyl group, such as a 2-propynyl group, a 2-butynyl group, a3-butynyl group, a 4-heptynyl group, a 1-methyl-2-propynyl group, a1,1-dimethyl-2-propynyl group, a 1-methyl-3-butynyl group, a1-methyl-4-heptynyl group, etc.; an alkoxyalkyl group, such as amethoxymethyl group, an ethoxymethyl group, a methoxyethyl group, anethoxyethyl group, an n-propoxyethyl group, an n-butoxyethyl group, amethoxypropyl group, an ethoxypropyl group, etc.; an aralkyl group, suchas a benzyl group, a 4-methylbenzyl group, a 4-tert-butylbenzyl group, a4-fluorobenzyl group, a 4-chlorobenzyl group, a 1-phenylethan-1-ylgroup, a 2-phenylethan-1-yl group, a 3-phenylpropan-1-yl group, etc.; anaryl group, such as a phenyl group, a 2-methylphenyl group, a3-methylphenyl group, a 4-methylphenyl group, a 4-tert-butylphenylgroup, a 2-fluorophenyl group, a 4-fluorophenyl group, a2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group, a4-trifluoromethylphenyl group, a 4-fluoro-2-trifluoromethylphenyl group,a 4-fluoro-3-trifluoromethylphenyl group, a 2,6-difluorophenyl group, a3,5-difluorophenyl group, a 2,4,6-trifluorophenyl group, a2,3,5,6-tetrafluorophenyl group, a perfluorophenyl group, etc.; and thelike.

In the case of n=1, of the foregoing, L is preferably a methyl group, anethyl group, an n-propyl group, an n-butyl group, an isopropyl group, asec-butyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a vinyl group, a1-propen-1-yl group, a 2-propen-1-yl group, a 2-buten-1-yl group, a3-buten-1-yl group, a 1-propen-2-yl group, a 1-buten-2-yl group, a2-methyl-2-propen-1-yl group, a 3,3-difluoro-2-propen-1-yl group, a4,4-difluoro-3-buten-1-yl group, a 3,3-dichloro-2-propen-1-yl group, a4,4-dichloro-3-buten-1-yl group, a 2-propynyl group, a 2-butynyl group,a 3-butynyl group, a 1-methyl-2-propynyl group, a1,1-dimethyl-2-propynyl group, a 2,3,5,6-tetrafluorophenyl group, or aperfluorophenyl group; and more preferably a vinyl group, a1-propen-1-yl group, a 2-propen-1-yl group, a 2-buten-1-yl group, a1-propen-2-yl group, a 3,3-difluoro-2-propen-1-yl group, a4,4-difluoro-3-buten-1-yl group, a 2-propynyl group, a 2-butynyl group,a 3-butynyl group, or a 1-methyl-2-propynyl group.

(ii) In the case of n=2:

There are suitably exemplified a straight-chain alkylene group, such asan ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, etc.; a branchedalkylene group, such as a propane-1,2-diyl group, a butane-1,3-diylgroup, a butane-2,3-diyl group, a 2-methylpropane-1,2-diyl group, a2,2-dimethylpropane-1,3-diyl group, etc.; a haloalkylene group, such asa 2,2-difluoropropano-1,3-diyl group, a2,2,3,3-tetrafluorobutane-1,4-diyl group, a2,2,3,3,4,4-hexafluoropentane-1,5-diyl group, a2,2,3,3,4,4,5,5-octafluorohexane-1,6-diyl group, a2,2-dichloropropane-1,3-diyl group, a 2,2,3,3-tetrachlorobutene-1,4-diylgroup, etc.; an alkenylene group, such as a 2-butene-1,4-diyl group, a2-pentene-1,5-diyl group, a 3-hexene-1,6-diyl group, a 3-hexene-2,5-diylgroup, a 2,5-dimethyl-3-hexene-2,5-diyl group, etc.; an alkynylenegroup, such as a 2-butyne-1,4-diyl group, a 2-pentyne-1,5-diyl group, a3-hexyne-1,6-diyl group, a 3-hexyne-2,5-diyl group, a2,5-dimethyl-3-hexyne-2,5-diyl group, etc.; a cycloalkylene group, suchas a cyclopentane-1,2-diyl group, a cyclopentane-1,3-diyl group, acyclohexane-1,2-diyl group, a cyclohexane-1,3-diyl group, acycloheptane-1,3-diyl group, a cyclohexane-1,4-diyl group, acycloheptane-1,4-diyl group, etc.; a connecting group having an ethergroup, such as —CH₂CH₂OCH₂CH₂—, —CH₂CH₂OCH₂CH₂OCH₂CH₂—,—CH₂CH₂CH₂OCH₂CH₂CH₂—, —CH(CH₃)CH₂OCH₂CH(CH₃)—, etc.; a connecting grouphaving a thioether bond, such as —CH₂CH₂SCH₂CH₂—, —CH₂CH₂CH₂SCH₂CH₂CH₂—,etc.; a connecting group having an S(═O)₂ bond, such as—CH₂CH₂S(═O)₂CH₂CH₂—, —CH₂CH₂CH₂S(═O)₂CH₂CH₂CH₂—, etc.; and an aromaticconnecting group, such as a benzene-1,2-diyl group, a benzene-1,3-diylgroup, a benzene-1,4-diyl group, etc.

In the case of n=2, of the foregoing, L is preferably an ethylene group,a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a propane-1,2-diyl group, abutane-2,3-diyl group, a 2,2-dimethylpropane-1,3-diyl group, a2-butene-1,4-diyl group, a 3-hexene-2,5-diyl group, a 2-butyne-1,4-diylgroup, a 3-hexyne-2,5-diyl group, a cyclohexane-1,2-diyl group, acyclohexane-1,4-diyl group, a cycloheptane-1,2-diyl group,—CH₂CH₂OCH₂CH₂—, —CH₂CH₂S(═O)₂CH₂CH₂—, or a benzene-1,4-diyl group, andmore preferably a 2-butene-1,4-diyl group or a 2-butyne-1,4-diyl group.

(iii) In the case of n=3:

There are suitably exemplified groups having the following structures.(“*” in the following structures represents a bonding site.)

As the compound represented by the foregoing general formula (I-1),specifically, there are suitably exemplified the following compounds.

Among the aforementioned compounds, as the compound represented by thegeneral formula (I-1), the compounds having any one of the structuralformulae of 1 to 4, 6, 7, 12 to 15, 19 to 23, 26, 27, 29 to 31, 33, 34,41, 42, 46 to 49, 81, 82, 84, 85, 88, 89, 112, 115 to 131, 133 to 136,138, 140 to 143, 146, 147, and 148 are more preferred; the compoundshaving any one of the structural formulae of 19 to 21, 26, 29, 30, 33,46, 47, 81, 82, 84, 85, 88, 115 to 118, 123, 124, and 140 to 143 arestill more preferred; and 2-propenyl 2-oxo-1,3-dioxolane-4-carboxylate(structural formula 21), 2-propynyl 2-oxo-1,3-dioxolane-4-carboxylate(structural formula 29), 2-propynyl5-fluoro-2-oxo-1,3-dioxolane-4-carboxylate (structural formula 116),2-propynyl 4-fluoro-2-oxo-1,3-dioxolane-4-carboxylate (structuralformula 118), di(2-propenyl) 2-oxo-1,3-dioxolane-4,5-dicarboxylate(structural formula 123), di(2-propynyl)2-oxo-1,3-dioxolane-4,5-dicarboxylate (structural formula 124),2-butene-1,4-diyl bis(2-oxo-1,3-dioxolane-4-carboxylate) (structuralformula 140), and 2-butyne-1,4-diylbis(2-oxo-1,3-dioxolane-4-carboxylate) (structural formula 142) areespecially preferred.

In the nonaqueous electrolytic solution of the present invention, acontent of the carboxylic acid ester compound represented by theforegoing general formula (I-1) is preferably 0.001 to 30% by mass inthe nonaqueous electrolytic solution. So long as the content is 30% bymass or less, there is less concern that a surface film is excessivelyformed on an electrode, so that in the case of using a battery at a hightemperature and at a high voltage, the storage characteristics areworsened. So long as the content is 0.001% by mass or more, theformation of a surface film is sufficient, and in the case of using abattery at a high temperature and at a high voltage, an improving effectof the storage characteristics is enhanced. The content is preferably0.01% by mass or more, and more preferably 0.3% by mass or more in thenonaqueous electrolytic solution. An upper limit thereof is preferably20% by mass or less, more preferably 10% by mass or less, and especiallypreferably 5% by mass or less.

[Nonaqueous Electrolytic Solution of Embodiment 2]

According to the nonaqueous electrolytic solution of Embodiment 2 of thepresent invention, in the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent, the compoundrepresented by the foregoing general formula (I) wherein X is an —S(═O)—group, an —S(═O)₂— group, or a —CR⁶R⁷ group, and n is 1, morespecifically the carboxylic acid ester compound represented by theforegoing general formula (I-2) is contained in the nonaqueouselectrolytic solution.

Although the reasons why the nonaqueous electrolytic solution ofEmbodiment 2 is able to greatly improve the electrochemicalcharacteristics of an energy storage device when used at a hightemperature and at a high voltage are not always elucidated yet, thefollowing may be considered.

The compound represented by the general formula (I-2), which is used inEmbodiment 2, has an —S(═O)— group, an —S(═O)— group, or a —CR⁶R⁷ groupand at least one carboxylic acid ester group that is an electronattractive group. For this reason, as compared with the compounds nothaving a carboxylic acid ester group but having only the ring structureas described in PTLs 4 to 6, it may be considered that the reactivity onthe electrode becomes much higher, the compound represented by thegeneral formula (I-2) quickly reacts with active sites of both thepositive electrode and the negative electrode. Furthermore, it may beconsidered that in view of the fact that the carboxylic acid ester iscontained in the surface film, the compound forms a firmer surface film,improves the storage characteristics at a high temperature and at a highvoltage, and inhibits the gas generation to de caused due todecomposition of the solvent.

The carboxylic acid ester compound which is contained in the nonaqueouselectrolytic solution of Embodiment 2 is represented by the followinggeneral formula (I-2).

In the formula, each of R²¹ and R²² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR⁵ group, and when R²¹ andR²² are each an alkyl group, then R²¹ and R²² may be bonded to eachother to form a ring structure. R²³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and R²⁴ andR²¹ may be the same as or different from each other and represent analkyl group having 1 to 6 carbon atoms, in which at least one hydrogenatom may be substituted with a halogen atom, a cycloalkyl group having 3to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkenyl group having 2 to 6 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,or an aryl group having 6 to 12 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom. X¹ represents an—S(═O) group, an —S(═O)₂ group, or a —CR²⁶R²⁷ group, and each of R²⁶ andR²⁷ independently represents a hydrogen atom or an alkyl group having 1to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom.

As specific examples of R²¹ and R²², there are suitably exemplified ahydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom,a bromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a 3-pentyl group,a tert-butyl group, a tert-amyl group, etc.; a halogenated alkyl group,such as a fluoromethyl group, a difluoromethyl group, a trifluoromethylgroup, a 2-chloroethyl group, a 2-fluoroethyl group, a 2,2-difluoroethylgroup, a 2,2,2-trifluoroethyl group, a 3-fluoropropyl group, a3-chloropropyl group, a 3,3-difluoropropyl group, a3,3,3-trifluoropropyl group, a 2,2,3,3-tetrafluoropropyl group, a2,2,3,3,3-pentafluoropropyl group, etc.; a cycloalkyl group, such as acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, etc.; an alkenyl group, such as vinyl group,a 1-propen-1-yl group, a 2-propen-1-yl group, a 2-buten-1-yl group, a3-buten-1-yl group, a 4-penten-1-yl group, a 5-hexen-1-yl group, a1-propen-2-yl group, a 1-buten-2-yl group, a 2-methyl-2-propen-1-ylgroup, etc.; an alkynyl group, such as an ethynyl group, a 2-propynylgroup, a 2-butynyl group, a 3-butynyl group, a 4-heptynyl group, a1-methyl-2-propynyl group, a 1,1-dimethyl-2-propynyl group, a1-methyl-3-butynyl group, a 1-methyl-4-heptynyl group, etc.; an aralkylgroup, such as a benzyl group, a 4-methylbenzyl group, a4-tert-butylbenzyl group, a 4-fluorobenzyl group, a 4-chlorobenzylgroup, a 1-phenylethan-1-yl group, a 2-phenylethan-1-yl group, a3-phenylpropan-1-yl group, etc.; and an aryl group, such as a phenylgroup, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenylgroup, a 4-tert-butylphenyl group, a 2-fluorophenyl group, a4-fluorophenyl group, a 2-trifluoromethylphenyl group, a3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a4-fluoro-2-trifluoromethylphenyl group, a4-fluoro-3-trifluoromethylphenyl group, a 2,6-difluorophenyl group, a3,5-difluorophenyl group, a 2,4,6-trifluorophenyl group, a2,3,5,6-tetrafluorophenyl group, a perfluorophenyl group, etc.; and alsoa methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a cyclopentyloxycarbonylgroup, a cyclohexyloxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, abenzyloxycarbonyl group, a phenyloxycarbonyl group, a4-fluorophenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonylgroup, a 4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, a perfluorophenyloxycarbonylgroup, and the like.

Of the foregoing, R²¹ and R²² are preferably a hydrogen atom, a fluorineatom, a chlorine atom, a methyl group, an ethyl group, an n-propylgroup, an n-butyl group, an n-pentyl group, an n-hexyl group, anisopropyl group, a sec-butyl group, a tert-butyl group, atrifluoromethyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a cyclopentyl group, a cyclohexylgroup, a vinyl group, a 1-propen-1-yl group, a 2-propen-1-yl group, a2-buten-1-yl group, a 1-propen-2-yl group, a 2-methyl-2-propen-1-ylgroup, an ethynyl group, a 2-propynyl group, a 1-methyl-2-propynylgroup, a methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, aphenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonyl group, a4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, or aperfluorophenyloxycarbonyl group; and more preferably a hydrogen atom, afluorine atom, a methyl group, an ethyl group, a trifluoromethyl group,a methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a 2-propen-1-yloxycarbonyl group,or a 2-propynyloxycarbonyl group.

When R²¹ and R²² are each an alkyl group, as examples of a ringstructure which R²¹ and R²² may be bonded to each other, there aresuitably exemplified an ethane-1,2-diyl group, a propane-1,3-diyl group,a butane-1,4-diyl group, and a pentane-1,5-diyl group, with abutane-1,4-diyl group or a pentane-1,5-diyl group being preferred.

As specific examples of R²³, there are suitably exemplified a hydrogenatom; a halogen atom, such as a fluorine atom, a chlorine atom, abromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; and a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a pentan-3-ylgroup, a tert-butyl group, a tert-amyl group, etc. Above all, a hydrogenatom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group,an n-propyl group, an n-butyl group, an isopropyl group, a sec-butylgroup, or a tert-butyl group is preferred, with a hydrogen atom, afluorine atom, a methyl group, or an ethyl group being more preferred.

As specific examples of R²⁴, there are suitably exemplified astraight-chain alkyl group, such as a methyl group, an ethyl group, ann-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group,etc.; a branched alkyl group, such as an isopropyl group, a sec-butylgroup, a 2-pentyl group, a 3-pentyl group, a tert-butyl group, atert-amyl group, etc.; a halogenated alkyl group, such as a fluoromethylgroup, a difluoromethyl group, a 2-chloroethyl group, a 2-fluoroethylgroup, a 2,2-difluoroethyl group, a 2,2,2-trifluoroethyl group, a3-fluoropropyl group, a 3-chloropropyl group, a 3,3-difluoropropylgroup, a 3,3,3-trifluoropropyl group, a 2,2,3,3-tetrafluoropropyl group,a 2,2,3,3,3-pentafluoropropyl group, etc.; a cycloalkyl group, such as acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group, etc.; a halogenated cycloalkyl group, suchas a 4-fluorocyclohexyl group, a 4-chlorocyclohexyl group, etc.; analkenyl group, such as a vinyl group, a 1-propen-1-yl group, a2-propen-1-yl group, a 2-buten-1-yl group, a 3-buten-1-yl group, a4-penten-1-yl group, a 5-hexen-1-yl group, a 1-propen-2-yl group, a1-buten-2-yl group, a 2-methyl-2-propen-1-yl group, etc.; a haloalkenylgroup, such as a 3,3-difluoro-2-propen-1-yl group, a4,4-difluoro-3-buten-1-yl group, a 3,3-dichloro-2-propen-1-yl group, a4,4-dichloro-3-buten-1-yl group, etc.; an alkynyl group, such as a2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 4-heptynylgroup, a 1-methyl-2-propynyl group, a 1,1-dimethyl-2-propynyl group, a1-methyl-3-butynyl group, a 1-methyl-4-heptynyl group, etc.; analkoxyalkyl group, such as a methoxymethyl group, an ethoxymethyl group,a methoxyethyl group, an ethoxyethyl group, an n-propoxyethyl group, ann-butoxyethyl group, a methoxypropyl group, an ethoxypropyl group, etc.;an aralkyl group, such as a benzyl group, a 4-methylbenzyl group, a4-tert-butylbenzyl group, a 4-fluorobenzyl group, a 4-chlorobenzylgroup, a 1-phenylethan-1-yl group, a 2-phenylethan-1-yl group, a3-phenylpropan-1-yl group, etc.; an aryl group, such as a phenyl group,a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group,a 4-tert-butylphenyl group, a 2-fluorophenyl group, a 4-fluorophenylgroup, a 2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group,a 4-trifluoromethylphenyl group, a 4-fluoro-2-trifluoromethylphenylgroup, a 4-fluoro-3-trifluoromethylphenyl group, a 2,4-difluorophenylgroup, a 2,6-difluorophenyl group, a 3,5-difluorophenyl group, a2,4,6-trifluorophenyl group, a 2,3,5,6-tetrafluorophenyl group, aperfluorophenyl group, etc.; and the like.

Of the foregoing, R²⁴ is preferably a methyl group, an ethyl group, ann-propyl group, an n-butyl group, an isopropyl group, a sec-butyl group,a 2,2,2-trifluoroethyl group, a 2,2,3,3-tetrafluoropropyl group, acyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexylgroup, a vinyl group, a 1-propen-1-yl group, a 2-propen-1-yl group, a2-buten-1-yl group, a 3-buten-1-yl group, a 1-propen-2-yl group, a1-buten-2-yl group, a 2-methyl-2-propen-1-yl group, a3,3-difluoro-2-propen-1-yl group, a 4,4-difluoro-3-buten-1-yl group, a3,3-dichloro-2-propen-1-yl group, a 4,4-dichloro-3-buten-1-yl group, a2-propynyl group, a 2-butynyl group, a 3-butynyl group, a1-methyl-2-propynyl group, a 1,1-dimethyl-2-propynyl group, a4-fluoro-3-trifluoromethylphenyl group, or a perfluorophenyl group, andmore preferably a methyl group, an ethyl group, a 2,2,2-trifluoroethylgroup, a 2,2,3,3-tetrafluoropropyl group, a 2-propen-1-yl group, a2-propynyl group, a 2-butynyl group, or a 1-methyl-2-propynyl group.

X¹ represents an —S(═O) group, an —S(═O)₂ group, or a —CR²⁶R²⁷ group.Specific examples of R²⁶ and R²⁷ include a hydrogen atom; astraight-chain alkyl group, such as a methyl group, an ethyl group, ann-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group,etc.; a branched alkyl group, such as an isopropyl group, a sec-butylgroup, a 2-pentyl group, a 3-pentyl group, a tert-butyl group, atert-amyl group, etc.; or a halogenated alkyl group, such as atrifluoromethyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a perfluorobutyl group, a1,1,1,3,3,3-hexafluoroisopropyl group, etc., with a hydrogen atom or amethyl group being preferred, and it is more preferred that R²⁶ and R²⁷each are a hydrogen atom.

Among the foregoing, X¹ is more preferably an —S(═O) group or an —S(═O)₂group, and especially preferably an —S(═O)₂ group.

As the compound represented by the foregoing general formula (I-2),specifically, there are suitably exemplified the following compounds.

(A) In the case where X¹ is an —S(═O) group:

(B) In the case where X¹ is an —S(═O)₂ group:

(C) In the case where X¹ is a —CR²⁶R²⁷ group:

Among the aforementioned compounds, as the compound represented by thegeneral formula (I-2), the compounds having any one of the structuralformulae of A1 to A3, A7 to A17, A22 to A26, A30 to A40, A43, B1 to B4,B6, B12 to B13, B16 to B17, B20 to B22, B24, B26 to B33, B41 to B53, B63to B78, C1 to C3, C7 to C17, C22 to C26, C30 to C46, and C49 to C50 arepreferred; the compounds having any one of the structural formulae of A1to A2, A8, A9, A14 to A15, A31 to A36, A39, A40, B1 to B2, B13, B16, B26to B28, B65 to B70, B74 to B75, C1 to C2, C8, C9, C14, C31 to C35, C39to C40, and C49 to C50 are more preferred; and at least one selectedfrom methyl 1,3,2-dioxathiolane-4-carboxylate 2-oxide (structuralformula A1), ethyl 1,3,2-dioxathiolane-4-carboxylate 2-oxide (structuralformula A2), 2-propenyl 1,3,2-dioxathiolane-4-carboxylate 2-oxide(structural formula A8), 2-propynyl 1,3,2-dioxathiolane-4-carboxylate2-oxide (structural formula A9), 2,2,2-trifluoroethyl1,3,2-dioxathiolane-4-carboxylate 2-oxide (structural formula A14),methyl 5-fluoro1-1,3,2-dioxathiolane-4-carboxylate 2-oxide (structuralformula A31), dimethyl 1,3,2-dioxathiolane-4,5-dicarboxylate 2-oxide(structural formula A33), diethyl 1,3,2-dioxathiolane-4,5-dicarboxylate2-oxide (structural formula A34), methyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide (structural formula B1),ethyl 1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide (structural formulaB2), 2-propenyl 1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide(structural formula B13), 2-propynyl 1,3,2-dioxathiolane-4-carboxylate2,2-dioxide (structural formula B16), 2,2,2-trifluoroethyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide (structural formula B26),methyl 5-fluoro-1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide(structural formula B65), dimethyl 1,3,2-dioxathiolane-4,5-dicarboxylate2,2-dioxide (structural formula B68), diethyl1,3,2-dioxathiolane-4,5-dicarboxylate 2,2-dioxide (structural formulaB69), methyl 1,3-dioxolane-4-carboxylate (structural formula C1), ethyl1,3-dioxolane-4-carboxylate (structural formula C2), 2-propenyl1,3-dioxolane-4-carboxylate (structural formula C8), 2-propynyl1,3-dioxolane-4-carboxylate (structural formula C9),2,2,2-trifluoroethyl 1,3-dioxolane-4-carboxylate (structural formulaC14), methyl 5-fluoro-1,3-dioxolane-4-carboxylate (structural formulaC31), dimethyl 1,3-dioxolane-4,5-dicarboxylate (structural formula C33),diethyl 1,3-dioxolane-4,5-dicarboxylate (structural formula C34), anddimethyl 2,2-dimethyl-1,3-dioxolane-4,5-dicarboxylate (structuralformula C49) is especially preferred.

In the nonaqueous electrolytic solution of the present invention, acontent of the carboxylic acid ester compound represented by the generalformula (I-2) is preferably 0.001 to 10% by mass in the nonaqueouselectrolytic solution. So long as the content is 10% by mass or less,there is less concern that a surface film is excessively formed on anelectrode, so that in the case of using a battery at a high temperatureand at a high voltage, the storage characteristics are worsened. So longas the content is 0.001% by mass or more, the formation of a surfacefilm is sufficient, and in the case of using a battery at a hightemperature and at a high voltage, an improving effect of the storagecharacteristics is enhanced. The content is preferably 0.05% by mass ormore, and more preferably 0.3% by mass or more in the nonaqueouselectrolytic solution. An upper limit thereof is preferably 8% by massor less, more preferably 5% by mass or less, and especially preferably3% by mass or less.

[Nonaqueous Electrolytic Solution of Embodiment 3]

According to the nonaqueous electrolytic solution of Embodiment 3 of thepresent invention, in the nonaqueous electrolytic solution having anelectrolyte salt dissolved in a nonaqueous solvent, the compoundrepresented by the foregoing general formula (I) wherein X is an—S(═O)₂—R⁵—S(═O)₂— group, and n is 1 or 2, more specifically thecarboxylic acid ester compound represented by the foregoing generalformula (I-3) is contained in the nonaqueous electrolytic solution.

Although the reasons why the nonaqueous electrolytic solution ofEmbodiment 3 is able to greatly improve the electrochemicalcharacteristics of an energy storage device when used at a hightemperature and at a high voltage are not always elucidated yet, thefollowing may be considered.

In view of the fact that the compound represented by the general formula(I-3), which is used in Embodiment 3, has a hetero ring which isreductively decomposed at the α-position of the carbonyl group to form asurface film, it has high reactivity and quickly reacts with activesites of both a positive electrode and a negative electrode, therebyforming a firmer surface film. Therefore, it may be considered that notonly the storage characteristics at a high temperature and at a highvoltage are improved, but also the gas generation to be caused due todecomposition of the solvent is inhibited.

The carboxylic acid ester compound which is contained in the nonaqueouselectrolytic solution of Embodiment 3 is represented by the followinggeneral formula (I-3).

In the formula, each of R³¹ and R³² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,an aryl group having 6 to 12 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, or a —C(═O)—OR³⁴group. R³³ represents a hydrogen atom, a halogen atom, or an alkyl grouphaving 1 to 6 carbon atoms, and m represents 1 or 2.

When m is 1, then L³ and R³⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, in whichat least one hydrogen atom may be substituted with a halogen atom, acycloalkyl group having 3 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an alkenyl grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, an alkynyl group having 3 to 6 carbonatoms, an alkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkylgroup having 2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, or an aryl group having 6 to 12 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, and whenm is 2, then L³ represents an alkylene group having 2 to 8 carbon atoms,an alkenylene group having 4 to 8 carbon atoms, or an alkynylene grouphaving 4 to 8 carbon atoms, at least one hydrogen atom of L³ may besubstituted with a halogen atom, and R³⁴ is the same as described above.

X² represents an —S(═O)₂—R³⁵—S(═O)₂— group, and R³⁵ represents analkylene group having 1 to 4 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom or an alkyl grouphaving 1 to 4 carbon atoms.

In the foregoing general formula (I-3), each of R³¹ and R³² isindependently preferably a hydrogen atom, a halogen atom, an alkyl grouphaving 1 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR³⁴ group, and morepreferably a hydrogen atom, a halogen atom, an alkyl group having 1 to 4carbon atoms, in which at least one hydrogen atom may be substitutedwith a halogen atom, or a —C(═O)—OR³⁴ group.

R³³ is preferably a hydrogen atom or a halogen atom, and more preferablya hydrogen atom. m represents 1 or 2, and preferably 1. When m is 1,then L³ and R³⁴ may be the same as or different from each other and arepreferably an alkyl group having 1 to 6 carbon atoms, in which at leastone hydrogen atom may be substituted with a halogen atom, a cycloalkylgroup having 3 to 6 carbon atoms, in which at least one hydrogen atommay be substituted with a halogen atom, an alkenyl group having 2 to 6carbon atoms, in which at least one hydrogen atom may be substitutedwith a halogen atom, an alkynyl group having 3 to 6 carbon atoms, or anaryl group having 6 to 12 carbon atoms, in which at least one hydrogenatom may be substituted with a halogen atom, and more preferably analkenyl group having 2 to 6 carbon atoms or an alkynyl group having 3 to6 carbon atoms. When m is 2, then L^(a) is preferably an alkylene grouphaving 2 to 6 carbon atoms, an alkenylene group having 4 to 8 carbonatoms, or an alkynylene group having 4 to 8 carbon atoms, and morepreferably an alkylene group having 2 to 4 carbon atoms, an alkenylenegroup having 4 to 6 carbon atoms, or an alkynylene group having 4 to 6carbon atoms.

R³⁵ is preferably an alkylene group having 1 to 2 carbon atoms, in whichat least one hydrogen atom may be substituted with a fluorine atom or amethyl group, and more preferably a methylene group.

As specific examples of R³¹ and R³², there are suitably exemplified ahydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom,a bromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a 3-pentyl group,a tert-butyl group, a tert-amyl group, etc.; a halogenated alkyl group,such as a fluoromethyl group, a difluoromethyl group, a trifluoromethylgroup, a 2-chloroethyl group, a 2-fluoroethyl group, a 2,2-difluoroethylgroup, a 2,2,2-trifluoroethyl group, a 3-fluoropropyl group, a3-chloropropyl group, a 3,3-difluoropropyl group, a3,3,3-trifluoropropyl group, a 2,2,3,3-tetrafluoropropyl group, a2,2,3,3,3-pentafluoropropyl group, etc.; and an aryl group, such as aphenyl group, a 2-methylphenyl group, a 3-methylphenyl group, a4-methylphenyl group, a 4-tert-butylphenyl group, a 2-fluorophenylgroup, a 4-fluorophenyl group, a 2-trifluoromethylphenyl group, a3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a4-fluoro-2-trifluoromethylphenyl group, a4-fluoro-3-trifluoromethylphenyl group, a 2,6-difluorophenyl group, a3,5-difluorophenyl group, a 2,4,6-trifluorophenyl group, a2,3,5,6-tetrafluorophenyl group, a perfluorophenyl group, etc.; and alsoa methoxycarbonyl group, an ethoxycarbonyl group, a2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a cyclopentyloxycarbonylgroup, a cyclohexyloxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, abenzyloxycarbonyl group, a phenyloxycarbonyl group, a4-fluorophenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonylgroup, a 4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, a perfluorophenyloxycarbonylgroup, and the like.

Of the foregoing, R³¹ and R³² are preferably a hydrogen atom, a fluorineatom, a chlorine atom, a methyl group, an ethyl group, an n-propylgroup, an n-butyl group, an n-pentyl group, an n-hexyl group, anisopropyl group, a sec-butyl group, a tert-butyl group, atrifluoromethyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a methoxycarbonyl group, anethoxycarbonyl group, a 2,2,2-trifluoroethoxycarbonyl group, a2,2,3,3-tetrafluoropropoxycarbonyl group, a vinyloxycarbonyl group, a1-propen-1-yloxycarbonyl group, a 2-propen-1-yloxycarbonyl group, a2-propynyloxycarbonyl group, a 1-methyl-2-propynyloxycarbonyl group, aphenyloxycarbonyl group, a 2-trifluoromethylphenyloxycarbonyl group, a4-fluoro-3-trifluoromethylphenyloxycarbonyl group, a2,3,5,6-tetrafluorophenyloxycarbonyl group, or aperfluorophenyloxycarbonyl group; and more preferably a hydrogen atom, afluorine atom, a methyl group, an ethyl group, a trifluoromethyl group,a 2-propen-1-yloxycarbonyl group, or a 2-propynyloxycarbonyl group.

As specific examples of R³³, there are suitably exemplified a hydrogenatom; a halogen atom, such as a fluorine atom, a chlorine atom, abromine atom, etc.; a straight-chain alkyl group, such as a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, etc.; and a branched alkyl group, such as anisopropyl group, a sec-butyl group, a 2-pentyl group, a pentan-3-ylgroup, a tert-butyl group, a tert-amyl group, etc. Above all, a hydrogenatom, a fluorine atom, a chlorine atom, a methyl group, an ethyl group,an n-propyl group, an n-butyl group, an isopropyl group, a sec-butylgroup, or a tert-butyl group is preferred, with a hydrogen atom, afluorine atom, a methyl group, or an ethyl group being more preferred.

As specific examples of L³, there are suitably exemplified the followinggroups.

(i) In the case of m=1:

There are suitably exemplified a straight-chain alkyl group, such as amethyl group, an ethyl group, an n-propyl group, an n-butyl group, ann-pentyl group, an n-hexyl group, etc.; a branched alkyl group, such asan isopropyl group, a sec-butyl group, a 2-pentyl group, a 3-pentylgroup, a tert-butyl group, a tert-amyl group, etc.; a halogenated alkylgroup, such as a fluoromethyl group, a difluoromethyl group, a2-chloroethyl group, a 2-fluoroethyl group, a 2,2-difluoroethyl group, a2,2,2-trifluoroethyl group, a 3-fluoropropyl group, a 3-chloropropylgroup, a 3,3-difluoropropyl group, a 3,3,3-trifluoropropyl group, a2,2,3,3-tetrafluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group,etc.; a cycloalkyl group, such as a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group,etc.; a halogenated cycloalkyl group, such as a 4-fluorocyclohexylgroup, a 4-chlorocyclohexyl group, etc.; an alkenyl group, such as avinyl group, a 1-propen-1-yl group, a 2-propen-1-yl group, a2-buten-1-yl group, a 3-buten-1-yl group, a 4-penten-1-yl group, a5-hexen-1-yl group, a 1-propen-2-yl group, a 1-buten-2-yl group, a2-methyl-2-propen-1-yl group, etc.; a haloalkenyl group, such as a3,3-difluoro-2-propen-1-yl group, a 4,4-difluoro-3-buten-1-yl group, a3,3-dichloro-2-propen-1-yl group, a 4,4-dichloro-3-buten-1-yl group,etc.; an alkynyl group, such as a 2-propynyl group, a 2-butynyl group, a3-butynyl group, a 4-heptynyl group, a 1-methyl-2-propynyl group, a1,1-dimethyl-2-propynyl group, a 1-methyl-3-butynyl group, a1-methyl-4-heptynyl group, etc.; an alkoxyalkyl group, such as amethoxymethyl group, an ethoxymethyl group, a methoxyethyl group, anethoxyethyl group, an n-propoxyethyl group, an n-butoxyethyl group, amethoxypropyl group, an ethoxypropyl group, etc.; a cyanoalkyl group,such as a cyanomethyl group, a 2-cyanoethyl group, a 3-cyanopropylgroup, a 4-cyanobutyl group. etc.; an aralkyl group, such as a benzylgroup, a 4-methylbenzyl group, a 4-tert-butylbenzyl group, a4-fluorobenzyl group, a 4-chlorobenzyl group, a 1-phenylethan-1-ylgroup, a 2-phenylethan-1-yl group, a 3-phenylpropan-1-yl group, etc.; anaryl group, such as a phenyl group, a 2-methylphenyl group, a3-methylphenyl group, a 4-methylphenyl group, a 4-tert-butylphenylgroup, a 2-fluorophenyl group, a 4-fluorophenyl group, a2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group, a4-trifluoromethylphenyl group, a 4-fluoro-2-trifluoromethylphenyl group,a 4-fluoro-3-trifluoromethylphenyl group, a 2,6-difluorophenyl group, a3,5-difluorophenyl group, a 2,4,6-trifluorophenyl group, a2,3,5,6-tetrafluorophenyl group, a perfluorophenyl group, etc.; and thelike.

In the case of m=1, of the foregoing, L³ is preferably a methyl group,an ethyl group, an n-propyl group, an n-butyl group, an isopropyl group,a sec-butyl group, a 2,2,2-trifluoroethyl group, a2,2,3,3-tetrafluoropropyl group, a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a vinyl group, a1-propen-1-yl group, a 2-propen-1-yl group, a 2-buten-1-yl group, a3-buten-1-yl group, a 1-propen-2-yl group, a 1-buten-2-yl group, a2-methyl-2-propen-1-yl group, a 3,3-difluoro-2-propen-1-yl group, a4,4-difluoro-3-buten-1-yl group, a 3,3-dichloro-2-propen-1-yl group, a4,4-dichloro-3-buten-1-yl group, a 2-propynyl group, a 2-butynyl group,a 3-butynyl group, a 1-methyl-2-propynyl group, a1,1-dimethyl-2-propynyl group, a 2,3,5,6-tetrafluorophenyl group, or aperfluorophenyl group; and more preferably a methyl group, an ethylgroup, a 2,2,2-trifluoroethyl group, a 2,2,3,3-tetrafluoropropyl group,a 2-propen-1-yl group, a 2-propynyl group, a 2-butynyl group, or a1-methyl-2-propynyl group.

(ii) In the case of m=2:

There are suitably exemplified a straight-chain alkylene group, such asan ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, etc.; a branchedalkylene group, such as a propane-1,2-diyl group, a butane-1,3-diylgroup, a butane-2,3-diyl group, a 2-methylpropane-1,2-diyl group, a2,2-dimethylpropane-1,3-diyl group, etc.; a haloalkylene group, such asa 2,2-difluoropropane-1,3-diyl group, a2,2,3,3-tetrafluorobutane-1,4-diyl group, a2,2,3,3,4,4-hexafluoropentane-1,5-diyl group, a2,2,3,3,4,4,5,5-octafluorohexane-1,6-diyl group, a2,2-dichloropropane-1,3-diyl group, a 2,2,3,3-tetrachlorobutene-1,4-diylgroup, etc.; an alkenylene group, such as a 2-butene-1,4-diyl group, a2-pentene-1,5-diyl group, a 3-hexene-1,6-diyl group, a 3-hexene-2,5-diylgroup, a 2,5-dimethyl-3-hexene-2,5-diyl group, etc.; and an alkynylenegroup, such as a 2-butyne-1,4-diyl group, a 2-pentyne-1,5-diyl group, a3-hexyne-1,6-diyl group, a 3-hexyne-2,5-diyl group, a2,5-dimethyl-3-hexyne-2,5-diyl group, etc.

In the case of m=2, of the foregoing, L³ is preferably an ethylenegroup, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, a propane-1,2-diylgroup, a butane-2,3-diyl group, a 2,2-dimethylpropane-1,3-diyl group, a2-butene-1,4-diyl group, a 3-hexene-2,5-diyl group, a 2-butyne-1,4-diylgroup, or a 3-hexyne-2,5-diyl group; and more preferably a2-buten-1,4-diyl group or a 2-butyne-1,4-diyl group.

As specific examples of X², there are suitably exemplified abis(sulfonyl)methyl group, a 1,1-bis(sulfonyl)ethyl group, a1,1-bis(sulfonyl)propyl group, a 1,1-bis(sulfonyl)butyl group, a2,2-bis(sulfonyl)propyl group, a 2,2-bis(sulfonyl)butyl group, a3,3-bis(sulfonyl)pentyl group, a bis(sulfonyl)fluoromethyl group, abis(sulfonyl)difluoromethyl group, a 1,2-bis(sulfonyl)ethyl group, a1,2-bis(sulfonyl)propyl group, a 2,3-bis(sulfonyl)butyl group, a1,3-bis(sulfonyl)propyl group, and a 1,4-bis(sulfonyl)butyl group. Amongthose, a bis(sulfonyl)methyl group, a 1,1-bis(sulfonyl)ethyl group, abis(sulfonyl)fluoromethyl group, or a 1,2-bis(sulfonyl)ethyl group ispreferred, with a bis(sulfonyl)methyl group being more preferred.

As the carboxylic acid ester compound represented by the foregoinggeneral formula (I-3), specifically, there are suitably exemplified thefollowing compounds.

Among the aforementioned compounds, as the compound represented by thegeneral formula (I-3), the compounds having any one of the structuralformulae of D1 to D4, D6, D11 to D13, D17, D18, D20 to D22, D24 to D26,D30, D31, D37 to D40, D49 to D64, and D73 to D75 are more preferred; thecompounds having any one of the structural formulae of D1, D2, D13, D17,D24, D25, D49 to D55, D58, and D59 are still more preferred; and methyl1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide (structuralformula D1), ethyl 1,5,2,4-dioxadithiepane-6-carboxylate2,2,4,4-tetraoxide (structural formula D2), 2-propenyl1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide (structuralformula D13), 2-propynyl 1,5,2,4-dioxadithiepane-6-carboxylate2,2,4,4-tetraoxide (structural formula D17), 2,2,2-trifluoroethyl1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide (structuralformula D24), methyl 1,5,2,4-dioxadithiepane-7-fluoro-6-carboxylate2,2,4,4-tetraoxide (structural formula D49), dimethyl1,5,2,4-dioxadithiepane-6,7-dicarboxylate 2,2,4,4-tetraoxide (structuralformula D53), and diethyl 1,5,2,4-dioxadithiepane-6,7-dicarboxylate2,2,4,4-tetraoxide (structural formula D54) are especially preferred.

In the nonaqueous electrolytic solution of the present invention, acontent of the carboxylic acid ester compound represented by theforegoing general formula (I-3) is preferably 0.001 to 10% by mass inthe nonaqueous electrolytic solution. So long as the content is 10% bymass or less, there is less concern that a surface film is excessivelyformed on an electrode, so that in the case of using a battery at a hightemperature and at a high voltage, the storage characteristics areworsened. So long as the content is 0.001% by mass or more, theformation of a surface film is sufficient, and in the case of using abattery at a high temperature and at a high voltage, an improving effectof the storage characteristics is enhanced. The content is preferably0.01% by mass or more, and more preferably 0.3% by mass or more in thenonaqueous electrolytic solution. An upper limit thereof is preferably8% by mass or less, more preferably 7% by mass or less, and especiallypreferably 5% by mass or less.

[Nonaqueous Solvent]

As the nonaqueous solvent which is used for the nonaqueous electrolyticsolution of the present invention, there are suitably exemplified one ormore selected from cyclic carbonates, linear esters, lactones, ethers,and amides. In order that the electrochemical characteristics may besynergistically improved at a high temperature, it is preferred toinclude a linear ester, it is more preferred to include a linearcarbonate, and it is most preferred to include both a cyclic carbonateand a linear carbonate.

The term “linear ester” is used as a concept including a linearcarbonate and a linear carboxylic acid ester.

As the cyclic carbonate, there is exemplified one or more selected fromethylene carbonate (EC), propylene carbonate (PC), 1,2-butylenecarbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC),trans- or cis-4,5-difluoro-1,3-dioxolan-2-one (the both will behereunder named generically as “DFEC”), vinylene carbonate (VC), vinylethylene carbonate (VEC), and 4-ethynyl-1,3-dioxolan-2-one (EEC). One ormore selected from ethylene carbonate, propylene carbonate,4-fluoro-1,3-dioxolan-2-one, vinylene carbonate, and4-ethynyl-1,3-dioxolan-2-one (EEC) are more suitable.

Use of at least one of cyclic carbonates having an unsaturated bond,such as a carbon-carbon double bond, a carbon-carbon triple bond, etc.,or a fluorine atom is preferred because the electrochemicalcharacteristics are much more improved at a high temperature, and it ismore preferred to contain both a cyclic carbonate having an unsaturatedbond, such as a carbon-carbon double bond, a carbon-carbon triple bond,etc., and a cyclic carbonate having a fluorine atom. As the cycliccarbonate having an unsaturated bond, such as a carbon-carbon doublebond, a carbon-carbon triple bond, etc., VC, VEC, or EEC is morepreferred, and as the cyclic carbonate having a fluorine atom, FEC orDFEC is more preferred.

A content of the cyclic carbonate having an unsaturated bond, such as acarbon-carbon double bond, a carbon-carbon triple bond, etc., ispreferably 0.07% by volume or more, more preferably 0.2% by volume ormore, and still more preferably 0.7% by volume or more relative to atotal volume of the nonaqueous solvent, and when an upper limit thereofis preferably 7% by volume or less, more preferably 4% by volume orless, and still more preferably 2.5% by volume or less, stability of asurface film can be much more increased at a high temperature withoutimpairing Li ion permeability, and hence, such is preferred.

A content of the cyclic carbonate having a fluorine atom is preferably0.07% by volume or more, more preferably 4% by volume or more, and stillmore preferably 7% by volume or more relative to a total volume of thenonaqueous solvent, and when an upper limit thereof is preferably 35% byvolume or less, more preferably 25% by volume or less, and still morepreferably 15% by volume or less, stability of a surface film can bemuch more increased at a high temperature without impairing Li ionpermeability, and hence, such is preferred.

In the case where the nonaqueous solvent includes both the cycliccarbonate having an unsaturated bond, such as a carbon-carbon doublebond, a carbon-carbon triple bond, etc., and the cyclic carbonate havinga fluorine atom, the content of the cyclic carbonate having anunsaturated bond, such as a carbon-carbon double bond, a carbon-carbontriple bond, etc., is preferably 0.2% by volume or more, more preferably3% by volume or more, and still more preferably 7% by volume or morerelative to the content of the cyclic carbonate having a fluorine atom,and when an upper limit thereof is preferably 40% by volume or less,more preferably 30% by volume or less, and still more preferably 15% byvolume or less, stability of a surface film can be much more increasedat a high temperature without impairing Li ion permeability, and hence,such is especially preferred.

When the nonaqueous solvent includes both ethylene carbonate and thecyclic carbonate having an unsaturated bond, such as a carbon-carbondouble bond, a carbon-carbon triple bond, etc., stability of a surfacefilm to be formed on an electrode at a high temperature is increased,and hence, such is preferred. A content of ethylene carbonate and thecyclic carbonate having an unsaturated bond, such as a carbon-carbondouble bond, a carbon-carbon triple bond, etc., is preferably 3% byvolume or more, more preferably 5% by volume or more, and still morepreferably 7% by volume relative to a total volume of the nonaqueoussolvent. An upper limit thereof is preferably 45% by volume or less,more preferably 35% by volume or less, and still more preferably 25% byvolume or less.

These solvents may be used solely; in the case where a combination oftwo or more of the solvents is used, the electrochemical characteristicsat a high temperature are more improved, and hence, such is preferred;and use of a combination of three or more thereof is especiallypreferred. As suitable combinations of these cyclic carbonates, EC andPC; EC and VC; PC and VC; VC and FEC; EC and FEC; PC and FEC; FEC andDFEC; EC and DFEC; PC and DFEC; VC and DFEC; VEC and DFEC; VC and EEC;EC and EEC; EC, PC and VC; EC, PC and FEC; EC, VC and FEC; EC, VC andVEC; EC, VC and EEC; EC, EEC and FEC; PC, VC and FEC; EC, VC and DFEC;PC, VC and DFEC; EC, PC, VC and FEC; EC, PC, VC and DFEC; and the likeare preferred. Among the aforementioned combinations, combinations, suchas EC and VC; EC and FEC; PC and FEC; EC, PC and VC; EC, PC and FEC; EC,VC and FEC; EC, VC and EEC; EC, EEC and FEC; PC, VC and FEC; EC, PC, VCand FEC; etc., are more preferred.

In the case of Embodiment 2, namely in the case of using the carboxylicacid ester compound represented by the foregoing general formula (I-2),combinations including PC, such as PC and FEC; EC, PC and VC; EC, PC andFEC; PC, VC and FEC; EC, PC, VC and FEC; etc., are still more preferredbecause battery characteristics at a high voltage are improved.

As the linear ester, there are suitably exemplified one or moreasymmetric linear carbonates selected from methyl ethyl carbonate (MEC),methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methylbutyl carbonate, and ethyl propyl carbonate; one or more symmetriclinear carbonates selected from dimethyl carbonate (DMC), diethylcarbonate (DEC), dipropyl carbonate, and dibutyl carbonate; one or morelinear carboxylic acid esters selected from methyl pivalate (MPiv),ethyl pivalate (EPiv), propyl pivalate (PPiv), methyl propionate (MP),ethyl propionate (EP), propyl propionate (PP), methyl acetate (MA), andethyl acetate (EA); one or more asymmetric fluorinated linear carbonatesselected from methyl (2,2,2-trifluoroethyl) carbonate (MTFEC), ethyl(2,2,2-trifluoroethyl) carbonate, fluoromethyl (methyl) carbonate(FMMC), methyl (2,2,3,3-tetrafluoropropyl) carbonate (MTEFPC), ethyl(2,2,3,3-tetrafluoropropyl) carbonate, 2-fluoroethyl (methyl) carbonate(2-FEMC), and difluoromethyl (fluoromethyl) carbonate; and one or moresymmetric fluorinated linear carbonates selected from bis(2-fluoroethyl)carbonate, bis(2,2,3,3-tetrafluoropropyl) carbonate,bis(2,2,2-trifluoroethyl) carbonate, and bis(fluoromethyl) carbonate.

Among the aforementioned linear esters, linear esters having a methylgroup selected from linear carbonates, such as dimethyl carbonate (DMC),methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methylisopropyl carbonate (MIPC), methyl butyl carbonate, etc.; and linearcarboxylic acid esters, such as methyl propionate (MP), ethyl propionate(EP), propyl propionate (PP), methyl acetate (MA), ethyl acetate (EA),etc., are preferred, and linear carbonates having a methyl group areespecially preferred.

In the case of using a linear carbonate, it is preferred to use two ormore thereof. Furthermore, it is more preferred that both the symmetriclinear carbonate and the asymmetric linear carbonate are included, andit is still more preferred that a content of the symmetric linearcarbonate is more than a content of the asymmetric linear carbonate.

Although the content of the linear ester is not particularly limited, itis preferred to use the linear ester in an amount in the range of from60 to 90% by volume relative to a total volume of the nonaqueoussolvent. When the content is 60% by volume or more, the viscosity of thenonaqueous electrolytic solution does not become excessively high, andwhen it is 90% by volume or less, there is less concern that anelectroconductivity of the nonaqueous electrolytic solution isdecreased, whereby the electrochemical characteristics at a hightemperature are worsened, and therefore, it is preferred that thecontent of the linear ester falls within the aforementioned range.

From the viewpoint of improving the electrochemical characteristics at ahigh voltage, it is preferred that at least one selected from symmetricfluorinated linear carbonates and asymmetric fluorinated linearcarbonates is included, and an asymmetric fluorinated linear carbonatehaving a methyl group, which is selected from methyl(2,2,2-trifluoroethyl) carbonate (MTFEC), 2-fluoroethyl (methyl)carbonate (2-FEMC), methyl (2,2,3,3-tetrafluoropropyl) carbonate(MTEFPC), and difluoromethyl (fluoromethyl) carbonate, is morepreferred.

A proportion of the volume occupied by the symmetric linear carbonate inthe linear carbonate is preferably 51% by volume or more, and morepreferably 55% by volume or more. An upper limit thereof is preferably95% by volume or less, and more preferably 85% by volume or less. It isespecially preferred that dimethyl carbonate is included in thesymmetric linear carbonate. It is more preferred that the asymmetriclinear carbonate has a methyl group, and methyl ethyl carbonate isespecially preferred. The aforementioned case is preferred because theelectrochemical characteristics at a high temperature are much moreimproved.

As for a proportion of the cyclic carbonate and the linear ester, fromthe viewpoint of improving the electrochemical characteristics at a hightemperature, a ratio of the cyclic carbonate to the linear ester (volumeratio) is preferably from 10/90 to 45/55, more preferably from 15/85 to40/60, and especially preferably from 20/80 to 35/65.

As other nonaqueous solvents, there are suitably exemplified one or moreselected from cyclic ethers, such as tetrahydrofuran,2-methyltetrahydrofuran, 1,4-dioxane, etc.; linear ethers, such as1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-butoxyethane, etc.; amides,such as dimethylformamide, etc.; sulfones, such as sulfolane, etc.; andlactones, such as γ-butyrolactone (GBL), γ-valerolactone,α-angelicalactone, etc.

The aforementioned nonaqueous solvents are generally mixed and used forthe purpose of achieving appropriate physical properties. As for acombination thereof, for example, there are suitably exemplified acombination of a cyclic carbonate and a linear carbonate, a combinationof a cyclic carbonate and a linear carboxylic acid ester, a combinationof a cyclic carbonate, a linear carbonate, and a lactone, a combinationof a cyclic carbonate, a linear carbonate, and an ether, a combinationof a cyclic carbonate, a linear carbonate, and a linear carboxylic acidester, and the like.

For the purpose of much more improving stability of a surface film at ahigh temperature, it is preferred to further add other additives in thenonaqueous electrolytic solution.

As specific examples of other additives, there are exemplified compoundsof the following (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile,succinonitrile, glutaronitrile, adiponitrile, pimelonitrile,suberonitrile, and sebaconitrile.

(B) Aromatic compounds having a branched alkyl group, such ascyclohexylbenzene, fluorocyclohexylbenzene compounds (e.g.,1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, and1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene,1-fluoro-4-tert-butylbenzene, etc., and aromatic compounds, such asbiphenyl, terphenyl (including o-, m-, and p-forms), diphenyl ether,fluorobenzene, difluorobenzene (including o-, m-, and p-forms), anisole,2,4-difluoroanisole, a partial hydride of terphenyl (e.g.,1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane,and o-cyclohexylbiphenyl), etc.

(C) One or more isocyanate compounds selected from methyl isocyanate,ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylenediisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate,1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and2-isocyanatoethyl methacrylate.

(D) One or more triple bond-containing compounds selected from2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate,2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynylvinylsulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate,di(2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyloxalate, di(2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate,2-butyne-1,4-diyl diformate, and 2,4-hexadiyne-1,6-diyldimethanesulfonate.

(E) One or more cyclic or linear S═O group-containing compounds selectedfrom sultones, such as 1,3-propanesultone, 1,3-butanesultone,2,4-butanesultone, 1,4-butanesultone, 1,3-propenesultone,2,2-dioxide-1,2-oxathiolane-4-yl acetate,5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, etc.; cyclic sulfites,such as ethylene sulfite, hexahydrobenzo[1,3,2]dioxathiolane-2-oxide(also called 1,2-cyclohexanediol cyclic sulfite),5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide,4-(methylsulfonylmethyl)-1,3,2-dioxathiolane-2-oxide, etc.; sulfonicacid esters, such as butane-2,3-diyl dimethanesulfonate, butane-1,4-diyldimethanesulfonate, methylene methanedisulfonate, dimethylmethanedisulfonate, pentafluorophenyl methanesulfonate, etc.; andvinylsulfone compounds, such as divinylsulfone,1,2-bis(vinylsulfonyl)ethane, bis(2-vinylsulfonylethyl) ether, etc.

(F) Cyclic acetal compounds, such as 1,3-dioxolane, 1,3-dioxane,1,3,5-trioxane, etc.

(G) One or more phosphorus-containing compounds selected from trimethylphosphate, tributyl phosphate, trioctyl phosphate,tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methylphosphate, bis(2,2,2-trifluoroethyl) ethyl phosphate,bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate,bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate,bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate,bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate,(2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl)methyl phosphate,tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, methylmethylenebisphosphonate, ethyl methylenebisphosphonate, methylethylenebisphosphonate, ethyl ethylenebisphosphonate, methylbutylenebisphosphonate, ethyl butylenebisphosphonate, methyl2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate,methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate,2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl2-(diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate,ethyl 2-(dimethoxyphosphoryl)acetate, methyl2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate,2-propynyl 2-(dimethoxyphosphoryl)acetate, 2-propynyl2-(diethoxyphosphoryl)acetate, methyl pyrophosphate, and ethylpyrophosphate.

(H) Linear carboxylic acid anhydrides, such as acetic anhydride,propionic anhydride, etc., and cyclic acid anhydrides, such as succinicanhydride, maleic anhydride, 3-allylsuccinic anhydride, glutaricanhydride, itaconic anhydride, 3-sulfo-propionic anhydride, etc.

(I) Cyclic phosphazene compounds, such asmethoxypentafluorocyclotriphosphazene,ethoxypentafluorocyclotriphosphazene,phenoxypentafluorocyclotriphosphazene,ethoxyheptafluorocyclotetraphosphazene, etc.

Of the foregoing, when at least one selected from (A) the nitriles, (B)the aromatic compounds, and (C) the isocyanate compounds is included,the electrochemical characteristics at a high temperature and at a highvoltage are much more improved, and hence, such is preferred.

Of (A) the nitriles, one or more selected from succinonitrile,glutaronitrile, adiponitrile, and pimelonitrile are more preferred.

Of (B) the aromatic compounds, one or more selected from biphenyl,terphenyl (including o-, m-, and p-forms), fluorobenzene,cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene are morepreferred; and one or more selected from biphenyl, o-terphenyl,fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are especiallypreferred.

Of (C) the isocyanate compounds, one or more selected from hexamethylenediisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate,and 2-isocyanatoethyl methacrylate are more preferred.

A content of each of the aforementioned additives (A) to (C) ispreferably 0.01 to 7% by mass in the nonaqueous electrolytic solution.When the content falls within this range, a surface film is sufficientlyformed without causing an excessive increase of the thickness, andstability of the surface film at a high temperature is much moreimproved. The content is more preferably 0.05% by mass or more, andstill more preferably 0.1% by mass or more in the nonaqueouselectrolytic solution, and an upper limited thereof is more preferably5% by mass or less, and still more preferably 3% by mass or less.

When (D) the triple bond-containing compound, (E) the cyclic or linearS═O group-containing compound selected from sultones, cyclic sulfites,sulfonic acid esters, and vinylsulfones, (F) the cyclic acetal compound,(G) the phosphorus-containing compound, (H) the cyclic acid anhydride,or (I) the cyclic phosphazene compound is included, stability of asurface film at a high temperature is much more improved, and hence,such is preferred.

As (D) the triple bond-containing compound, one or more selected from2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynylmethanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl2-(methanesulfonyloxy)propionate, di(2-propynyl) oxalate, methyl2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyldimethanesulfonate are preferred; and one or more selected from2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl2-(methanesulfonyloxy)propionate, di(2-propynyl) oxalate, and2-butyne-1,4-diyl dimethanesulfonate are more preferred.

It is preferred to use (E) the cyclic or linear S═O group-containingcompound selected from sultones, cyclic sulfites, sulfonic acid esters,and vinylsulfones, (provided that triple bond-containing compounds arenot included).

As the cyclic S═O group-containing compound, there are suitablyexemplified one or more selected from sultones, such as1,3-propanesultone, 1,3-butanesultone, 1,4-butanesultone,2,4-butanesultone, 1,3-propenesultone, 2,2-dioxide-1,2-oxathiolane-4-ylacetate, 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, etc.; sulfonicacid esters, such as methylene methanedisulfonate, etc.; and cyclicsulfites, such as ethylene sulfite,4-(methylsulfonylmethyl)-1,3,2-dioxathiolane 2-oxide, etc.

As the linear S═O group-containing compound, there are suitablyexemplified one or more selected from butane-2,3-diyldimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethylmethanedisulfonate, pentafluorophenyl methanesulfonate, divinylsulfone,and bis(2-vinylsulfonylethyl) ether.

Of the aforementioned cyclic or linear S═O group-containing compounds,one or more selected from 1,3-propanesultone, 1,4-butanesultone,2,4-butanesultone, 2,2-dioxide-1,2-oxathiolane-4-yl acetate,5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, butane-2,3-diyldimethanesulfonate, pentafluorophenyl methanesulfonate, anddivinylsulfone are more preferred.

As (F) the cyclic acetal compound, 1,3-dioxolane and 1,3-dioxane arepreferred, and 1,3-dioxane is more preferred.

As (G) the phosphorus-containing compound, tris(2,2,2-trifluoroethyl)phosphate, tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, methyl2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate,methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate,2-propynyl 2-(dimethylphosphoryl)acetate, 2-propynyl2-(diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate,ethyl 2-(dimethoxyphosphoryl)acetate, methyl2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate,2-propynyl 2-(dimethoxyphosphoryl)acetate, and 2-propynyl2-(diethoxyphosphoryl)acetate are preferred; andtris(2,2,2-trifluoroethyl) phosphate,tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, ethyl2-(diethylphosphoryl)acetate, 2-propynyl 2-(dimethylphosphoryl)acetate,2-propynyl 2-(diethylphosphoryl)acetate, ethyl2-(diethoxyphosphoryl)acetate, 2-propynyl2-(dimethoxyphosphoryl)acetate, and 2-propynyl2-(diethoxyphosphoryl)acetate are more preferred.

As (H) the cyclic acid anhydride, succinic anhydride, maleic anhydride,and 3-allylsuccinic anhydride are preferred, and succinic anhydride and3-allylsuccinic anhydride are more preferred.

As (I) the cyclic phosphazene compound, cyclic phosphazene compounds,such as methoxypentafluorocyclotriphosphazene,ethoxypentafluorocyclotriphosphazene,phenoxypentafluorocyclotriphosphazene, etc., are preferred, andmethoxypentafluorocyclotriphosphazene andethoxypentafluorocyclotriphosphazene are more preferred.

A content of each of the aforementioned additives (D) to (I) ispreferably 0.001 to 5% by mass in the nonaqueous electrolytic solution.When the content falls within this range, a surface film is sufficientlyformed without causing an excessive increase of the thickness, andstability of the surface film at a high temperature is much moreimproved. The content is more preferably 0.01% by mass or more, andstill more preferably 0.1% by mass or more in the nonaqueouselectrolytic solution, and an upper limited thereof is more preferably3% by mass or less, and still more preferably 2% by mass or less.

For the purpose of much more improving stability of a surface film at ahigh temperature, it is preferred that at least one selected fromlithium salts having an oxalate skeleton, lithium salts having aphosphate skeleton, and lithium salts having an S═O group is included inthe nonaqueous electrolytic solution.

As specific examples of the lithium salt, there are suitably exemplifiedat least one lithium salt having an oxalate skeleton, which is selectedfrom lithium bis(oxalatc)borato (LiBOB), lithium difluoro(oxalatc)borate(LiDFOB), lithium tetrafluoro(oxalate)phosphate (LiTFOP), and lithiumdifluorobis(oxalate)phosphate (LiDFOP); a lithium salt having aphosphate skeleton, such as LiPO₂F₂, Li₂PO₃F, etc.; and at least onelithium salt having an S═O group, which is selected from lithiumtrifluoro((methanesulfonyl)oxy)borate (LiTFMSB), lithiumpentafluoro((methanesulfonyl)oxy)phosphate (LiPFMSP), lithium methylsulfate (LMS), lithium ethyl sulfate (LES), lithium 2,2,2-trifluoroethylsulfate (LFES), and FSO₃Li.

Among those, it is more preferred that a lithium salt selected fromLiBOB, LiDFOB, LiTFOP, LiDFOP, LiPO₂F₂, LiTFMSB, LMS, LES, LFES, andFSO₃Li is included.

A total content of at least one selected from lithium salts having anoxalate skeleton, lithium salts having a phosphate skeleton, and lithiumsalts having an S═O group, in particular at least one lithium saltselected from LiBOB, LiDFOB, LiTFOP, LiDFOP, LiPO₂F₂, Li₂PO₃F, LiTFMSB,LiPFMSP, LMS, LES, LFES, and FSO₃Li, is preferably 0.001 to 10% by massin the nonaqueous electrolytic solution. When the content is 10% by massor less, there is less concern that a surface film is excessively formedon an electrode, so that the storage characteristics are worsened, andwhen it is 0.001% by mass or more, the formation of a surface film issufficient, and in the case of using a battery at a high temperature andat a high voltage, an improving effect of the characteristics isenhanced. The content is preferably 0.05% by mass or more, morepreferably 0.1% by mass or more, and still more preferably 0.3% by massor more in the nonaqueous electrolytic solution. An upper limit thereofis preferably 5% by mass or less, more preferably 3% by mass or less,and especially preferably 2% by mass or less.

(Lithium Salt)

As the electrolyte salt which is used in the present invention, thereare suitably exemplified the following lithium salts.

As the lithium salt, there are suitably exemplified inorganic lithiumsalts, such as LiPF₆, LiBF₄, LiClO₄, etc.; linear fluoroalkylgroup-containing lithium salts, such as LiN(SO₂F)₂, LiN(SO₂CF₃)₂,LiN(SO₂C₂F₅)₂, LiCF₃SO₃, LiC(SO₂CF₃)₃, LiPF₄(CF₃)₂, LiPF₃(C₂F₃)₂,LiPF₃(CF₃)₃, LiPF₃(iso-C₃F₇)₃, LiPF₅(iso-C₃F₇), etc.; and cyclicfluoroalkylene chain-containing lithium salts, such as (CF₂)₂(SO₂)₂NLi,(CF₂)₃(SO₂)₂NLi, etc.; and the like. At least one lithium salt selectedfrom these lithium salts is suitably exemplified, and one or morethereof may be solely or in admixture.

Among those, one or more selected from LiPF₆, LiBF₄, LiN(SO₂CF₃)₂,LiN(SO₂C2F₅)₂, and LiN(SO₂F)₂ are preferred, and it is most preferred touse LiPF₆.

In general, a concentration of the lithium salt is preferably 0.3 M ormore, more preferably 0.7 M or more, and still more preferably 1.1 M ormore relative to the nonaqueous solvent. An upper limit thereof ispreferably 2.5 M or less, more preferably 2.0 M or less, and still morepreferably 1.6 M or less.

As for a suitable combination of these lithium salts, the case ofincluding LiPF₆ and further including at least one lithium salt selectedfrom LiBF₄. LiN(SO₂CF₃)₂, and LiN(SO₂F)₂ in the nonaqueous electrolyticsolution is preferred.

When a proportion of the lithium salt other than LiPF_(c) occupying inthe nonaqueous solvent is 0.001 M or more, an improving effect of theelectrochemical characteristics in the case of using the battery at ahigh temperature is liable to be exhibited, and when it is 1.0 M orless, there is less concern that the improving effect of theelectrochemical characteristics in the case of using the battery at ahigh temperature is worsened, and hence, such is preferred. Theproportion is preferably 0.01 M or more, especially preferably 0.03 M ormore, and most preferably 0.04 M or more. An upper limit thereof ispreferably 0.8 M or less, more preferably 0.6 M or less, and especiallypreferably 0.4 M or less.

[Production of Nonaqueous Electrolytic Solution]

The nonaqueous electrolytic solution of the present invention may beobtained, for example, by mixing the aforementioned nonaqueous solvent,adding the aforementioned electrolyte salt thereto, and further addingthe carboxylic acid ester compound represented by the foregoing generalformula (I), in particular the carboxylic acid ester compoundrepresented by the foregoing general formula (I-1), (I-2), or (I-3) tothe resulting nonaqueous electrolytic solution.

At this time, the nonaqueous solvent to be used and the compounds to beadded to the nonaqueous electrolytic solution are preferably purified inadvance to decrease impurities as far as possible within the range wherethe productivity is not remarkably worsened.

The nonaqueous electrolytic solution of the present invention may beused in first to fourth energy storage devices shown below, in which thenonaqueous electrolytic solution may be used as the nonaqueouselectrolyte not only in the form of a liquid but also in the form ofgel. Furthermore, the nonaqueous electrolytic solution of the presentinvention may also be used for a solid polymer electrolyte. Above all,the nonaqueous electrolytic solution is preferably used in the firstenergy storage device using a lithium salt as the electrolyte salt(namely, for a lithium battery) or in the fourth energy storage device(namely, for a lithium ion capacitor), more preferably used in a lithiumbattery, and still more preferably used in a lithium secondary battery.

[First Storage Device (Lithium Battery)]

The lithium battery as referred to in the present specification is ageneric name for a lithium primary battery and a lithium secondarybattery. In the present specification, the term “lithium secondarybattery” is used as a concept also including a so-called lithium ionsecondary battery. The lithium battery of the present invention includesa positive electrode, a negative electrode, and the aforementionednonaqueous electrolytic solution having an electrolyte salt dissolved ina nonaqueous solvent. Other constitutional members than the nonaqueouselectrolytic solution, such as the positive electrode, the negativeelectrode, etc., may be used without being particularly limited.

For example, examples of a positive electrode active material used for alithium secondary battery include a complex metal oxide containinglithium and one or more selected from cobalt, manganese, and nickel.These positive electrode active materials may be used solely or incombination of two or more thereof.

Examples of the lithium complex metal oxide include one or more selectedfrom LiCoO₂, LiMn₂O₄, LiNiO₂, LiCo_(1-x)Ni_(x)O₂ (0.01<x<1),LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂, LiNi_(1/2)Mn_(3/2)O₄, andLiCo_(0.98)Mg_(0.02)O₂. These materials may be used as a combination,such as a combination of LiCoO₂ and LiMn₂O₄, a combination of LiCoO₂ andLiNiO₂, and a combination of LiMn₂O₄ and LiNiO₂.

For improving the safety on overcharging and the cycle characteristics,and for enabling the use at a charge potential of 4.3 V or more, a partof the lithium complex metal oxide may be substituted with otherelements. For example, a part of cobalt, manganese, or nickel may besubstituted with at least one element selected from Sn, Mg, Fe, Ti, Al,Zr, Cr, V, Ga, Zn, Cu, Bi, Mo, and La, a part of 0 may be substitutedwith S or F, or the oxide may be coated with a compound containing anyof such other elements.

Among those, a lithium complex metal oxide capable of being used at acharge potential of the positive electrode in a fully-charged state of4.3 V or more based on Li, such as LiCoO₂, LiMn₂O₄, and LiNiO₂, ispreferred; and a lithium complex metal oxide capable of being used at4.4 V or more, such as LiCo_(1-x)M_(x)O₂ (wherein M represents one ormore elements selected from Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, andCu, and 0.001≤x≤0.05), LiCo_(1/3)Ni_(1/3)Mn_(1/3)O₂,LiNi_(1/2)Mn_(3/2)O₄, and a solid solution of LiMnO₃ and LiMO₂ (whereinM represents a transition metal, such as Co, Ni, Mn, Fe, etc.), is morepreferred. The use of the lithium complex metal oxide capable of actingat a high charge voltage is liable to worsen the electrochemicalcharacteristics particularly in a broad temperature range due to thereaction with the electrolytic solution on charging, but in the lithiumsecondary battery according to the present invention, worsening of theelectrochemical characteristics can be inhibited. In particular, abattery with a positive electrode containing Mn tends to have anincreased resistance due to elution of Mn ions from the positiveelectrode, thereby providing the tendency of worsening theelectrochemical characteristics in a broad temperature range. However,the lithium secondary battery according to the present invention ispreferred because worsening of the electrochemical characteristics canbe inhibited.

Furthermore, a lithium-containing olivine-type phosphate may also beused as the positive electrode active material. In particular, alithium-containing olivine-type phosphate including one or more selectedfrom iron, cobalt, nickel, and manganese is preferred. As specificexamples thereof, there are exemplified one or more selected fromLiFePO₄, LiCoPO₄, LiNiPO₄, and LiMnPO₄. A part of such alithium-containing olivine-type phosphate may be substituted with otherelement. A part of iron, cobalt, nickel, or manganese may be substitutedwith one or more elements selected from Co, Mn, Ni, Mg, Al, B, Ti, V,Nb, Cu, Zn, Mo, Ca, Sr, W, Zr, and the like, or the phosphate may becoated with a compound containing any of these other elements or with acarbon material. Among those, LiFePO₄ and LiMnPO₄ are preferred. Thelithium-containing olivine-type phosphate may also be used, for example,in admixture with the aforementioned positive electrode active material.

Examples of the positive electrode for a lithium primary battery includeoxides or chalcogen compounds of one or more metal elements, such asCuO, Cu₂O, Ag₂O, Ag₂CrO₄, CuS, CuSO₄, TiO₂, TiS₂, SiO₂, SnO, V₂O₅,V₆O₁₂, VO_(x), Nb₂O₅, Bi₂O₃, Bi₂Pb₂O, Sb₂O₃, CrO₃, Cr₂O₃, MoO₃, WO₃,SeO₂, MnO₂, Mn₂O₃, Fe₂O₃, FeO, Fe₃O₄, Ni₂O₃, NiO, CoO₃, CoO, and thelike; a sulfur compound, such as SO₂, SOCl₂, etc.; and a carbon fluoride(graphite fluoride) represented by a general formula (CF_(x))_(n). Amongthose, MnO₂, V₂O₅, graphite fluoride, and the like are preferred.

In the case where when 10 g of the aforementioned positive electrodeactive material is dispersed in 100 mL of distilled water, a pH of asupernatant thereof is 10.0 to 12.5, the improving effect of theelectrochemical characteristics in a much broader temperature range isliable to be obtained, and hence, such is preferred. The case where thepH is 10.5 to 12.0 is more preferred.

In the case where Ni is included as an element in the positiveelectrode, the content of impurities, such as LiOH, etc., in thepositive electrode active material tends to increase, and the improvingeffect of the electrochemical characteristics in a much broadertemperature range is liable to be obtained, and hence, such ispreferred. The case where an atomic concentration of Ni in the positiveelectrode active material is 5 to 25 atomic % is more preferred, and thecase where the atomic concentration of Ni is 8 to 21 atomic % isespecially preferred.

An electroconductive agent of the positive electrode is not particularlylimited as far as it is an electron-conductive material that does notundergo chemical change. Examples thereof include graphite, such asnatural graphite (e.g., flaky graphite, etc.), artificial graphite,etc.; one or more carbon blacks selected from acetylene black, Ketjenblack, channel black, furnace black, lamp black, and thermal black; andthe like. The graphite and the carbon black may be appropriately mixedand used. An amount of the electroconductive agent added to a positiveelectrode mixture is preferably from 1 to 10% by mass, and especiallypreferably from 2 to 5% by mass.

The positive electrode can be produced in such a manner that thepositive electrode active material is mixed with an electroconductiveagent, such as acetylene black, carbon black, etc., and then mixed witha binder, such as polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), a copolymer of styrene and butadiene (SBR), a copolymerof acrylonitrile and butadiene (NBR), carboxymethyl cellulose (CMC), anethylene-propylene-diene terpolymer, etc., to which is then added ahigh-boiling point solvent, such as 1-methyl-2-pyrrolidone, etc.,followed by kneading to provide a positive electrode mixture, and thepositive electrode mixture is applied onto a collector, such as analuminum foil, a stainless steel-made lath plate, etc., dried, shapedunder pressure, and then heat-treated in vacuum at a temperature ofabout 50° C. to 250° C. for about 2 hours.

A density of the positive electrode except for the collector isgenerally 1.5 g/cm³ or more, and for the purpose of further increasing acapacity of the battery, the density is preferably 2 g/cm³ or more, morepreferably 3 g/cm³ or more, and still more preferably 3.6 g/cm³ or more.An upper limit thereof is preferably 4 g/cm³ or less.

As a negative electrode active material for a lithium secondary battery,one or more selected from lithium metal, a lithium alloy, a carbonmaterial capable of absorbing and releasing lithium [e.g., graphitizablecarbon, non-graphitizable carbon having a spacing of a (002) plane of0.37 nm or more, graphite having a spacing of the (002) plane of 0.34 nmor less, etc.], tin (elemental substance), a tin compound, silicon(elemental substance), a silicon compound, and a lithium titanatecompound, such as Li₄Ti₅O₁₂, etc., may be used.

Among the aforementioned negative electrode active materials, in theability of absorbing and releasing lithium ions, the use of ahigh-crystalline carbon material, such as artificial graphite, naturalgraphite, etc., is more preferred, and the use of a carbon materialhaving a graphite-type crystal structure in which a lattice (002)spacing (d₀₀₂) is 0.340 nm (nanometers) or less, and especially from0.335 to 0.337 nm, is still more preferred. In particular, the use ofartificial graphite particles having a bulky structure containing pluralflattened graphite fine particles that are aggregated or bondednon-parallel to each other, or graphite particles produced through aspheroidizing treatment of flaky natural graphite particles byrepeatedly applying a mechanical action, such as a compression force, afriction force, a shear force, etc., is preferred.

When a ratio I(110)/I(004) of a peak intensity I(110) of the (110) planeto a peak intensity I(004) of the (004) plane of the graphite crystalobtained through X-ray diffractometry of a negative electrode sheet thatis shaped under pressure to such an extent that a density of thenegative electrode except for the collector is 1.5 g/cm³ or more, is0.01 or more, the electrochemical characteristics are improved in a muchbroader temperature range, and hence, such is preferred.

The ratio I(110)/I(004) is more preferably 0.05 or more, and still morepreferably 0.1 or more. An upper limit of the ratio I(110)/I(004) of thepeak intensity is preferably 0.5 or less, and more preferably 0.3 orless because there may be the case where the crystallinity is worsenedto lower the discharge capacity of the battery due to an excessivetreatment.

When the high-crystalline carbon material (core material) is coated witha carbon material having lower crystallinity than the core material, theelectrochemical characteristics in a broad temperature range become muchmore favorable, and hence, such is preferred. The crystallinity of thecarbon material in the coating may be confirmed through TEM.

When the high-crystalline carbon material is used, there is a tendencythat it reacts with the nonaqueous electrolytic solution on charging,thereby worsening the electrochemical characteristics at a lowtemperature or a high temperature due to an increase of interfacialresistance. However, in the lithium secondary battery according to thepresent invention, the electrochemical characteristics in a broadtemperature range become favorable.

As the metal compound capable of absorbing and releasing lithium as anegative electrode active material, there are suitably exemplifiedcompounds containing at least one metal element, such as Si, Ge, Sn, Pb,P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, Sr, Ba, etc.The metal compound may be in any form including an elemental substance,an alloy, an oxide, a nitride, a sulfide, a boride, an alloy withlithium, and the like, and any of an elemental substance, an alloy, anoxide, and an alloy with lithium is preferred because the batterycapacity can be increased. Above all, compounds containing at least oneelement selected from Si, Ge, and Sn are preferred, and compoundscontaining at least one element selected from Si and Sn are morepreferred because the battery capacity can be increased.

The negative electrode can be produced in such a manner that the sameelectroconductive agent, binder, and high-boiling point solvent as inthe production of the positive electrode as described above are used andkneaded to provide a negative electrode mixture, and the negativeelectrode mixture is then applied on a collector, such as a copper foil,etc., dried, shaped under pressure, and then heat-treated in vacuum at atemperature of about from 50° C. to 250° C. for about 2 hours.

A density of the negative electrode except for the collector isgenerally 1.1 g/cm³ or more, and for the purpose of further increasing acapacity of the battery, the density is preferably 1.5 g/cm³ or more,and more preferably 1.7 g/cm³ or more. An upper limit thereof ispreferably 2 g/cm³ or less.

Examples of the negative electrode active material for a lithium primarybattery include lithium metal and a lithium alloy.

The structure of the lithium battery is not particularly limited, andmay be a coin-type battery, a cylinder-type battery, a prismaticbattery, a laminate-type battery, or the like, each having asingle-layered or multi-layered separator.

The separator for the battery is not particularly limited, and asingle-layered or laminated micro-porous film of a polyolefin, such aspolypropylene, polyethylene, etc., a woven fabric, a nonwoven fabric,and the like may be used.

The lithium secondary battery in the present invention has excellentelectrochemical characteristics in a broad temperature range even when afinal charging voltage is 4.2 V or more, particularly 4.3 V or more, andfurthermore, the characteristics are favorable even at 4.4 V or more. Afinal discharging voltage may be generally 2.8 V or more, and further2.5 V or more, and the final discharging voltage of the lithiumsecondary battery in the present invention may be 2.0 V or more. Anelectric current is not particularly limited, and in general, thebattery may be used within a range of from 0.1 to 30 C. The lithiumbattery in the present invention may be charged and discharged at from−40 to 100° C., and preferably from −10 to 80° C.

In the present invention, as a countermeasure against the increase inthe internal pressure of the lithium battery, there may also be adoptedsuch a method that a safety valve is provided in a battery cap, or acutout is provided in a component, such as a battery can, a gasket, etc.As a safety countermeasure for prevention of overcharging, a circuitcut-off mechanism capable of detecting the internal pressure of thebattery to cut off the current may be provided in the battery cap.

[Second Energy Storage Device (Electric Double Layer Capacitor)]

The second energy storage device of the present invention is an energystorage device including the nonaqueous electrolytic solution of thepresent invention and storing energy by utilizing an electric doublelayer capacitance in an interface between the electrolytic solution andthe electrode. One example of the present invention is an electricdouble layer capacitor. A most typical electrode active material whichis used in this energy storage device is active carbon. The double layercapacitance increases substantially in proportion to a surface area.

[Third Energy Storage Device]

The third energy storage device of the present invention is an energystorage device including the nonaqueous electrolytic solution of thepresent invention and storing energy by utilizing a doping/dedopingreaction of the electrode. Examples of the electrode active materialwhich is used in this energy storage device include a metal oxide, suchas ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide,copper oxide, etc., and a R-conjugated polymer, such as polyacene, apolythiophene derivative, etc. A capacitor using such an electrodeactive material is capable of storing energy following thedoping/dedoping reaction of the electrode.

[Fourth Energy Storage Device (Lithium Ion Capacitor)]

The fourth energy storage device of the present invention is an energystorage device including the nonaqueous electrolytic solution of thepresent invention and storing energy by utilizing intercalation oflithium ions into a carbon material, such as graphite, etc., as thenegative electrode. This energy storage device is called a lithium ioncapacitor (LIC). Examples of the positive electrode include oneutilizing an electric double layer between an active carbon electrodeand an electrolytic solution, one utilizing a doping/dedoping reactionof a n-conjugated polymer electrode, and the like. The electrolyticsolution contains at least a lithium salt, such as LiPF₆, etc.

One of the carboxylic acid ester compounds as a novel compound of thepresent invention is represented by the following general formula (II).

In the formula, each of R⁴¹ and R⁴² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,a cycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR⁴ group, and when R⁴¹ andR⁴² are each an alkyl group, then R⁴¹ and R⁴² may be bonded to eachother to form a ring structure. R⁴³ represents a hydrogen atom, ahalogen atom, or an alkyl group having 1 to 6 carbon atoms, and mrepresents 1 or 2.

When m is 1, then LU and R⁴¹ may be the same as or different from eachother and represent a halogenated alkyl group having 1 to 6 carbonatoms, in which at least one hydrogen atom is substituted with a halogenatom, a halogenated cycloalkyl group having 3 to 6 carbon atoms, inwhich at least one hydrogen atom is substituted with a halogen atom, analkenyl group having 2 to 6 carbon atoms, in which at least one hydrogenatom may be substituted with a halogen atom, an alkynyl group having 3to 6 carbon atoms, an alkoxyalkyl group having 3 to 6 carbon atoms, acyanoalkyl group having 2 to 6 carbon atoms, a halogenated aralkyl grouphaving 7 to 13 carbon atoms, in which at least one hydrogen atom issubstituted with a halogen atom, or a halogenated aryl group having 6 to12 carbon atoms, in which at least one hydrogen atom is substituted witha halogen atom, and when m is 2, then U represents an alkylene grouphaving 2 to 6 carbon atoms, in which at least one hydrogen atom issubstituted with a halogen atom, an alkenylene group having 4 to 8carbon atoms, or an alkynylene group having 4 to 8 carbon atoms, and R⁴⁴is the same as described above, provided that when m is 1, then U is nota 3-methyl-2-buten-1-yl group.

In the general formula (II), the substituents R⁴¹, R⁴², and R⁴³ aresynonymous with R¹, R², and R³ in the general formula (I), respectively.

m is corresponding to a part of n of the general formula (I) andrepresents 1 or 2. Detailed thereof have already been explained in theforegoing general formula (I), and hence, in this section, theexplanation is omitted in order to avoid overlapping. In this case, thesubstituents R⁴ and L of the general formula (I) can be designated asthe substituents R⁴⁴ and L⁴ of the general formula (II), respectively.

Specific carboxylic ester compounds represented by the foregoing generalformula (II) are the same as the specific compounds and preferredcompounds described with respect to the general formula (I), exclusiveof the compounds having any one of the structural formulae of 1 to 11,56 to 58, 61 to 63, 64 to 68, 83, 87, 89, 91, 93, 95, 91, 97, 101, 103,105, 107, 109, 111, 113, 115, 117, 119 to 121, 128 to 136, and 147 to149.

The carboxylic acid ester compound represented by the general formula(II) of the present invention may be synthesized by the following twomethods, but the present invention is not limited to these productionmethods.

(a) Dehydration Condensation Method:

The carboxylic acid ester compound is obtained by subjecting acarboxylic acid compound obtained by the method described inWO2013/092011 and an alcohol compound to dehydration condensation in asolvent or non-solvent in the presence of a dehydration condensingagent.

(b) Acid Chloride Method:

The carboxylic acid ester compound is obtained by allowing an acidchloride of a carboxylic acid compound to react with an alcohol compoundin a solvent in the presence or absence of a base.

Another one of the carboxylic acid ester compounds as a novel compoundof the present invention is represented by the following general formula(III).

In the formula, each of R⁵¹ and R⁵² independently represents a hydrogenatom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, an aryl group having 6 to 12carbon atoms, or a —C(═O)—OR⁵⁴ group, and when R⁵¹ and R⁵² are each analkyl group, then R⁵¹ and R⁵² may be bonded to each other to form a ringstructure. R⁵³ represents a hydrogen atom, a halogen atom, or an alkylgroup having 1 to 6 carbon atoms, and m represents 1 or 2.

When m is 1, then L⁵ and R⁵⁴ may be the same as or different from eachother and represent an alkyl group having 1 to 6 carbon atoms, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, or anaryl group having 6 to 12 carbon atoms, and when m is 2, then L⁵represents an alkylene group having 2 to 8 carbon atoms, an alkenylenegroup having 4 to 8 carbon atoms, or an alkynylene group having 4 to 8carbon atoms, at least one hydrogen atom of L⁵ may be substituted with ahalogen atom, and R⁵⁴ is the same as described above.

X³ represents an —S(═O)₂—R⁵⁵—S(═O)₂— group, and R⁵⁵ represents analkylene group having 1 to 4 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom or an alkyl grouphaving 1 to 4 carbon atoms.

At least one hydrogen atom of the alkyl group having 1 to 6 carbonatoms, the cycloalkyl group having 3 to 6 carbon atoms, the alkenylgroup having 2 to 6 carbon atoms, the alkynyl group having 3 to 6 carbonatoms, the alkoxyalkyl group having 2 to 6 carbon atoms, the cyanoalkylgroup having 2 to 6 carbon atoms, the aralkyl group having 7 to 13carbon atoms, or the aryl group having 6 to 12 carbon atoms as R⁵¹, R⁵²,R⁵⁴, or L⁵, may be substituted with a halogen atom.

Specific compounds represented by the foregoing general formula (III)are the same as the description of specific compounds and preferreddescription for the general formula (I).

The compound represented by the general formula (III) may be synthesizedby a method of allowing an alkanedisulfonyl dihalide compound to reactwith a corresponding diol compound in a solvent or non-solvent in thepresence of a base, but the present invention is not limited to such amethod.

As for effects of the compound represented by the general formula (III),for example, an effect as an additive for an energy storage device shownin the following Examples, but the invention is not limited thereto.

The compound represented by the general formula (III) is a novelcarboxylic acid ester compound, and in view of a special structurethereof, it includes an application as an electrolyte, and so on in thefields of general chemistry, particularly organic chemistry,electrochemistry, biochemistry, and polymer chemistry.

In consequence, the compound represented by the general formula (III) isa useful compound as intermediate raw materials of drugs, agriculturalchemicals, electronic materials, polymer materials, and the like, andalso as electronic materials.

EXAMPLES

Synthesis Examples of the carboxylic acid ester compound which is usedin the present invention and Examples of the electrolytic solution ofthe present invention are hereunder described, but it should not beconstrued that the present invention is limited to these SynthesisExamples and Examples.

Synthesis Example I-1 [Synthesis of 2-Propynyl2-Oxo-1,3-dioxolane-4-carboxylate (Synthetic Compound 1)]

7.1 g (0.054 mol) of 2-oxo-1,3-dioxolane-4-carboxylic acid, 30 mL ofethyl acetate, and 3.0 g (0.054 mol) of propargyl alcohol were added atroom temperature and then cooled to 10° C. To this solution, 12.4 g(0.065 mol) of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride was added at 10 to 20° C. over 10 minutes, followed bystirring at room temperature for 3 hours. The reaction solution waswashed with water and extracted with ethyl acetate, and the solvent wasconcentrated under reduced pressure. The resulting residue was purifiedby means of silica gel column chromatography (elution with ethylacetate/hexane=1/2), thereby obtaining 4.9 g (yield: 53%) of thetargeted 2-propynyl 2-oxo-1,3-dioxolane-4-carboxylate.

The obtained 2-propynyl 2-oxo-1,3-dioxolane-4-carboxylate was subjectedto ¹H-NMR and melting point measurement, thereby confirming itsstructure.

The results are shown below.

¹H-NMR (400 MHz, CDCl₃): δ=5.14 (dd, J=5.4 Hz, 9.0 Hz, 1H), S=4.86 (d,J=2.5 Hz, 2H), 8=4.71 (t, J=9.0 Hz, 1H), 8=4.56 (dd, J=5.4 Hz, 9.0 Hz,1H), 2.58 (t, J=2.5 Hz, 1H)

Melting point: 35° C.

Examples I-1 to I-46 and Comparative Examples I-1 to 1-3 [Production ofLithium Ion Secondary Battery]

94% by mass of LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂ and 3% by mass of acetyleneblack (electroconductive agent) were mixed and then added to and mixedwith a solution which had been prepared by dissolving 3% by mass ofpolyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone in advance,thereby preparing a positive electrode mixture paste. This positiveelectrode mixture paste was applied onto one surface of an aluminum foil(collector), dried, and treated under pressure, followed by cutting intoa predetermined size, thereby producing a positive electrode sheet in abelt-like form. A density of the positive electrode except for thecollector was 3.6 g/cm³.

10% by mass of silicon (elemental substance), 80% by mass of artificialgraphite (d₀₀₂=0.335 nm, negative electrode active material), and 5% bymass of acetylene black (electroconductive agent) were mixed and thenadded to and mixed with a solution which had been prepared by dissolving5% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidonein advance, thereby preparing a negative electrode mixture paste. Thisnegative electrode mixture paste was applied onto one surface of acopper foil (collector), dried, and treated under pressure, followed bycutting into a predetermined size, thereby producing a negativeelectrode sheet. A density of the negative electrode except for thecollector was 1.5 g/cm³.

The electrode sheet was analyzed by X-ray diffractometry, and a ratio[I(110)/I(004)] of the peak intensity I(110) of the (110) plane to thepeak intensity I(004) of the (004) plane of the graphite crystal was0.1.

The above-obtained positive electrode sheet, a micro-porouspolyethylene-made film separator and the above-obtained negativeelectrode sheet were laminated in this order, and the nonaqueouselectrolytic solution having each of compositions shown in Tables 1 and2 was added, thereby producing a laminate-type battery.

[Discharge Capacity Retention Rate after High-Temperature ChargedStorage]

<Initial Discharge Capacity>

In a thermostatic chamber at 25° C., the laminate-type battery producedby the aforementioned method was charged up to a final voltage of 4.35 Vwith a constant current of 1 C and under a constant voltage for 3 hoursand then discharged down to a final voltage of 2.75 V with a constantcurrent of 1 C, thereby determining an initial discharge capacity.

<High-Temperature Charged Storage Test>

Subsequently, in a thermostatic chamber at 60° C., this laminate-typebattery was charged up to a final voltage of 4.35 V with a constantcurrent of 1 C and under a constant voltage for 3 hours, and then storedfor 7 days while being kept at 4.35 V. Thereafter, the battery wasplaced in a thermostatic chamber at 25° C., and once discharged under aconstant current of 1 C to a final voltage of 2.75 V.

<Discharge Capacity after High-Temperature Charged Storage>

Further thereafter, the discharge capacity after the high-temperaturecharged storage was determined in the same manner as in the measurementof the initial discharge capacity.

<Discharge Capacity Retention Rate after High-Temperature ChargedStorage>

A discharge capacity retention rate (%) after the high-temperaturecharged storage was determined according to the following equation.

Discharge capacity retention rate (%) after high-temperature chargedstorage=(Discharge capacity after high-temperature chargedstorage)/(Initial discharge capacity)×100

[Evaluation of Gas Generation Amount after High-Temperature ChargedStorage]

A gas generation amount after the high-temperature charged storage wasmeasured by the Archimcdcan method. As for the gas generation amount, arelative gas generation amount was evaluated on the basis of definingthe gas generation amount of Comparative Example I-1 as 100%.

In addition, the production condition and battery characteristics ofeach of the batteries are shown in Tables 1 to 4.

In Table 2, LiBOB (Example I-25) is lithium bis(oxalate)borate, GBL(Example I-26) is γ-butyrolactone, and EA (Example I-27) is ethylacetate.

TABLE 11 Compound represented by formula (I-1) Composition ofelectrolyte Content in salt nonaqueous Discharge Composition ofnonaqueous electrolytic capacity Gas generation electrolytic solutionsolution retention rate amount (volume ratio of solvent) Kind (% bymass) (%) (%) Example I-1     Example I-2     Example I-3 1.15M LiPF₆EC/DMC/MEC (30/40/30) 1.15M LiPF₆ EC/MEC (30/70) 1.15M LiPF₆EC/VC/DMC/MEC (29/1/40/30)

 1      1      0.05 80     77     72 55     58     62 Example I-4 1.15MLiPF₆  0.1 76 58 EC/VC/DMC/MEC (29/1/40/30) Example I-5 1.15M LiPF₆   0.5 80 55 EC/VC/DMC/MEC (29/1/40/30) Example I-6 1.15M LiPF₆  1 82 52EC/VC/DMC/MEC (29/1/40/30) Example I-7 1.15M LiPF₆  3 76 57EC/VC/DMC/MEC (29/1/40/30) Example I-8 1.15M LiPF₆  5 72 63EC/VC/DMC/MEC (29/1/40/30) Example I-9 1.15M LiPF₆ 10 70 65EC/VC/DMC/MEC (29/1/40/30) Example I-10     Example I-11 1.15M LiPF₆EC/VC/DMC/MEC (29/1/40/30) 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

20     30 68     66 70     75

TABLE 2 Compound represented by formula (I-1) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example I-12 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 77 56 Example I-13 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 76 58 Example I-14 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 75 59 Example I-15 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 78 54 Example I-16 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 78 55 Example I-17 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 80 53 Example I-18 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 80 54 Example I-19 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 73 57 Example I-20 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 79 56 Example I-21 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 81 53 Example I-22 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 74 55 Example I-23 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 73 53 Example I-24 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 80 54 Example I-25 1.15M LiPF₆ + 0.05M LiBOB EC/FEC/VC/DMC/MEC(19/10/1/40/30)

1 84 52 Example I-26 1.15M LiPF₆ + 0.05M LiPO₂F₂ EC/VC/DMC/MEC/GBL(29/1/37/30/3)

1 82 51 Example I-27 1.1M LiPF₆ + 0.05M LES EC/VC/DMC/MEC/EA(29/1/35/30/5)

1 85 51

TABLE 3 Compound represented by formula (I-1) Composition of electrolyteContent in salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example I-28     Example I-29     Example I-30 1.15M LiPF₆ EC/VC/DMC/MEC(29/1/40/30) 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30) 1.15M LiPF₆EC/VC/DMC/MEC (29/1/40/30)

 0.1      0.5      1 70     74     76 65     62     59 Example I-311.15M LiPF₆  3 71 64 EC/VC/DMC/MEC (29/1/40/30) Example I-32 1.15M LiPF₆ 5 67 68 EC/VC/DMC/MEC (29/1/40/30) Example I-33 1.15M LiPF₆ 10 65 70EC/VC/DMC/MEC (29/1/40/30) Example I-34 1.15M LiPF₆ 20 66 73EC/VC/DMC/MEC (29/1/40/30) Example I-35 1.15M LiPF₆ 30 64 79EC/VC/DMC/MEC (29/1/40/30) Example I-36 1.15M LiPF₆ EC/VC/DMC/MEC(29/1/40/30)

 1 77 54 Example I-37 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

 1 81 54 Comparative 1.15M LiPF₆ None — 56 100  Example I-1EC/VC/DMC/MEC (29/1/40/30) Comparative Example I-2 1.15M LiPF₆EC/VC/DMC/MEC (29/1/40/30)

 1 55 101  Comparative Example I-3 1.15M LiPF₆ EC/VC/DMC/MEC(29/1/40/30)

 1 61 98

TABLE 4 Composition of electrolyte salt Compound represented byComposition of formula (I-1) nonaqueous Content in Dischargeelectrolytic nonaqueous Other additive (content capacity Gas solutionelectrolytic Group of in nonaqueous retention generation (volume ratioof solution other electrolytic solution (% by rate amount solvent) Kind(% by mass) additive mass)) (%) (%) Example I-38 Example I-39 ExampleI-40 Example I-41 1.15M LiPF₆ EC/VC/DMC/MEC (29/1/40/30)

1 A   B   C   D Adiponitrile (1)   Cyclohexylbenzene (2) + o-terphenyl(1) 1,6-Hexamethylene diisocyanate (1) 2-Butyne-1,4-diyldimethanesulfonate (1) 79   85   80   87 45   54   46   52 Example E5,5-Dimethyl- 81 49 I-42 1,2-oxathiolane-4-one 2,2-dioxide (0.5) ExampleF 1,3-Dioxane (1) 82 44 I-43 Example G Tris(2,2,2-trifluoroethyl) 81 46I-41 phosphate (1.5) Example H Succinic anhydride (1) 86 54 I-45 ExampleI Ethoxypentafluoro- 83 50 I-46 cyclotriphosphazene (1)

Examples I-47 and Comparative Example I-4

A positive electrode sheet was produced by using LiNi_(1/2)Mn_(3/2)O₄(positive electrode active material) in place of the positive electrodeactive material used in Example I-1 and Comparative Example I-1. 94% bymass of LiNi_(1/2)Mn_(3/2)O₄ coated with amorphous carbon and 3% by massof acetylene black (electroconductive agent) were mixed and then addedto and mixed with a solution which had been prepared by dissolving 3% bymass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone inadvance, thereby preparing a positive electrode mixture paste. Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example I-1 and Comparative Example I-1,except that this positive electrode mixture paste was applied onto onesurface of an aluminum foil (collector), dried, and treated underpressure, followed by cutting into a predetermined size, therebyproducing a positive electrode sheet; and that in evaluating thebattery, the final charging voltage and the final discharging voltagewere set to 4.9 V and 2.7 V, respectively. The results are shown inTable 5.

TABLE 5 Compound represented by formula (I-1) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example I-47 1.15M LiPF₆ EC/FEC/MEC/DEC (20/10/45/25)

1 77  62 Comparative None — 49 100 Example I-4

Example I-48 and Comparative Example I-5

A negative electrode sheet was produced by using lithium titanateLi₄Ti₅O₁₂ (negative electrode active material) in place of the negativeelectrode active material used in Example I-1 and Comparative ExampleI-1. 80% by mass of lithium titanate Li₄TiO₁₂ and 15% by mass ofacetylene black (electroconductive agent) were mixed and then added toand mixed with a solution which had been prepared by dissolving 5% bymass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone inadvance, thereby preparing a negative electrode mixture paste, Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example I-1 and Comparative Example I-1,except that this negative electrode mixture paste was applied onto onesurface of a copper foil (collector), dried, and treated under pressure,followed by cutting into a predetermined size, thereby producing anegative electrode sheet; that in evaluating the battery, the finalcharging voltage and the final discharging voltage were set to 2.8 V and1.2 V, respectively; and that the composition of the nonaqueouselectrolyte was changed to a predetermined composition. The results areshown in Table 6.

TABLE 6 Compound represented by formula (I-1) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example I-48 1.15M LiPF₆ PC/DEC (30/70)

1 89  49 Comparative None — 79 100 Example I-5

All of the lithium secondary batteries of Examples I-1 to I-46 asdescribed above are improved in the storage characteristics at a hightemperature and at a high voltage and inhibited in the gas generationamount, as compared with the lithium secondary batteries of ComparativeExample I-1 which is in the case of not containing the compoundrepresented by the general formula (I-1) and Comparative Examples I-2and I-3 which are in the case of adding the compounds described in PTLs1 and 2, respectively.

In the light of the above, it has become clear that the effects broughtin the case of using the energy storage device of the present inventionat a high voltage are peculiar effects brought in the case where thenonaqueous electrolytic solution contains the compound represented bythe general formula (I-1).

In addition, from the comparison of Example I-47 with ComparativeExample I-4 in the case of using lithium nickel manganate(LiNi_(1/2)Mn_(3/2)O₄) for the positive electrode and also from thecomparison of Example I-48 with Comparative Example I-5 in the case ofusing lithium titanate (Li₄Ti₅O₁₂) for the negative electrode, the sameeffects are brought.

In consequence, it is evident that the effects of the present inventionaccording to Embodiment 1 are not an effect relying upon a specifiedpositive electrode or negative electrode.

Furthermore, the nonaqueous electrolytic solution containing thecompound represented by the general formula (I-1) of the presentinvention also has an effect for improving the discharging properties inthe case of using a lithium primary battery at a high voltage.

Examples II-1 to II-25 and Comparative Examples II-1 to II-4 [Productionof Lithium Ion Secondary Battery]

94% by mass of LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂ and 3% by mass of acetyleneblack (electroconductive agent) were mixed and then added to and mixedwith a solution which had been prepared by dissolving 3% by mass ofpolyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone in advance,thereby preparing a positive electrode mixture paste. This positiveelectrode mixture paste was applied onto one surface of an aluminum foil(collector), dried, and treated under pressure, followed by cutting intoa predetermined size, thereby producing a positive electrode sheet in abelt-like form. A density of the positive electrode except for thecollector was 3.6 g/cm³.

10% by mass of silicon (elemental substance), 80% by mass of artificialgraphite (d₀₀₂=0.335 nm, negative electrode active material), and 5% bymass of acetylene black (electroconductive agent) were mixed and thenadded to and mixed with a solution which had been prepared by dissolving5% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidonein advance, thereby preparing a negative electrode mixture paste. Thisnegative electrode mixture paste was applied onto one surface of acopper foil (collector), dried, and treated under pressure, followed bycutting into a predetermined size, thereby producing a negativeelectrode sheet. A density of the negative electrode except for thecollector was 1.5 g/cm³.

The electrode sheet was analyzed by X-ray diffractometry, and a ratio[I(110)/I(004)] of the peak intensity I(110) of the (110) plane to thepeak intensity I(004) of the (004) plane of the graphite crystal was0.1.

The above-obtained positive electrode sheet, a micro-porouspolyethylene-made film separator and the above-obtained negativeelectrode sheet were laminated in this order, and the nonaqueouselectrolytic solution having each of compositions shown in Tables 7 and8 was added, thereby producing a laminate-type battery.

[Discharge Capacity Retention Rate after High-Temperature ChargedStorage]

<Initial Discharge Capacity>

In a thermostatic chamber at 25° C., the laminate-type battery producedby the aforementioned method was charged up to a final voltage of 4.35 Vwith a constant current of 1 C and under a constant voltage for 3 hoursand then discharged down to a final voltage of 2.75 V with a constantcurrent of 1 C, thereby determining an initial discharge capacity.

<High-Temperature Charged Storage Test>

Subsequently, in a thermostatic chamber at 65° C., this laminate-typebattery was charged up to a final voltage of 4.35 V with a constantcurrent of 1 C and under a constant voltage for 3 hours, and then storedfor 5 days while being kept at 4.35 V. Thereafter, the battery wasplaced in a thermostatic chamber at 25° C., and once discharged under aconstant current of 1 C to a final voltage of 2.75 V.

<Discharge Capacity after High-Temperature Charged Storage>

Further thereafter, the discharge capacity after the high-temperaturecharged storage was determined in the same manner as in the measurementof the initial discharge capacity.

<Discharge Capacity Retention Rate after High-Temperature ChargedStorage>

A discharge capacity retention rate (%) after the high-temperaturecharged storage was determined according to the following equation.

Discharge capacity retention rate (%) after high-temperature chargedstorage=(Discharge capacity after high-temperature chargedstorage)/(Initial discharge capacity)×100

[Evaluation of Gas Generation Amount after High-Temperature ChargedStorage]

A gas generation amount after the high-temperature charged storage wasmeasured by the Archimedean method. As for the gas generation amount, arelative gas generation amount was evaluated on the basis of definingthe gas generation amount of Comparative Example II-1 as 100%.

In addition, the production condition and battery characteristics ofeach of the batteries are shown in Tables 7 and 8.

In Table 7, GBL (Example II-14) is γ-butyrolactone, MPiv (Example II-15)is methyl pivalate, and MP (Example II-16) is methyl propionate.

TABLE 7 Compound represented by formula (I-2) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example II-1      Example II-2      Example II-3  1M LiPF₆ EC/PC/MEC/DEC(26/4/30/40) 1M LiPF₆ EC/MEC (30/70) 1M LiPF₆ EC/PC/VC/MEC/DEC(20/9/1/30/40)

1       1       0.01 71     67     63 64     67     72 Example II-4  1MLiPF₆ 0.1  72 64 EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-5  1M LiPF₆1   78 59 EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-6  1M LiPF₆ 4   7357 EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-7  1M LiPF₆EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   75 61 Example II-8  1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   81 60 Example II-9  1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   77 59 Example II-10 1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   79 58 Example II-11 1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   79 66 Example II-12 1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   76 63 Example II-13     Example II-14     Example II-15 1M LiPF₆ +0.05M LiFOP EC/PC/FEC/VC/DEC/MEC (16/3/10/1/45/25) 1M LiPF₆ + 0.05MLiPO₂F₂ EC/PC/VC/DEC/MEC/GBL (26/3/1/42/25/3) 1M LiPF₆ + 0.05M LESEC/PC/VC/DEC/MEC/MPiv (20/9/1/40/25/5)

1       1       1   81     80     83 58     55     54 Example II-160.70M LiPF₆ + 0.35M FSI 1   84 56 EC/PC/VC/DMC/MEC/MP (20/9/1/40/25/5)

TABLE 8 Compound represented by formula (I-2) Content in Composition ofelectrolyte salt nonaqueoua Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example II-17     Example II-18 1M LiPF₆ EC/PC/MEC/DMC (20/10/30/40) 1MLiPF₆ EC/MEC (30/70)

1       1   68     65 68     70 Example II-19 1M LiPF₆ 0.01 61 73EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-20 1M LiPF₆ 0.1  69 70EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-21 1M LiPF₆ 1   74 65EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-22 1M LiPF₆ 4   71 62EC/PC/VC/MEC/DEC (20/9/1/30/40) Example II-23 1M LiPF₆ EC/PC/VC/MEC/DEC(20/9/1/30/40)

1   73 68 Example II-24 1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   72 70 Example II-25 1M LiPF₆ EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   70 67 Comparative 1M LiPF₆ None 1   51 100  Example II-1EC/PC/VC/MEC/DEC (20/9/1/30/40) Comparative Example II-2 1M LiPF₆EC/PC/VC/MEC/DEC (20/9/1/30/40)

1   59 88 Comparative Example II-3 1M LiPF₆ EC/PC/VC/MEC/DEC(20/9/1/30/40)

1   54 92 Comparative Example II-4 1M LiPF₆ EC/PC/VC/MEC/DEC(20/9/1/30/40)

1   51 83

Examples II-26 and II-27 and Comparative Example II-5

A positive electrode sheet was produced by using LiNi_(1/2)Mn_(3/2)O₄(positive electrode active material) in place of the positive electrodeactive material used in Example II-1 and Comparative Example II-1. 94%by mass of LiNi_(1/2)Mn_(3/2)O₄ coated with amorphous carbon and 3% bymass of acetylene black (electroconductive agent) were mixed and thenadded to and mixed with a solution which had been prepared by dissolving3% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidonein advance, thereby preparing a positive electrode mixture paste. Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example II-1 and Comparative Example II-1,except that this positive electrode mixture paste was applied onto onesurface of an aluminum foil (collector), dried, and treated underpressure, followed by cutting into a predetermined size, therebyproducing a positive electrode sheet; and that in evaluating thebattery, the final charging voltage and the final discharging voltagewere set to 4.9 V and 2.7 V, respectively. The results are shown inTable 9.

In Table 9, FEC is 4-fluoro-1,3-dioxolan-2-one, and MTFEC is methyl(2,2,2-trifluoroethyl)carbonate.

TABLE 9 Compound represented by formula (I-2) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example II-26 1M LiPF₆ FEC/MTFEC (30/70)

1 71  75 Example II-27

1 64  78 Comparative None — 45 100 Example II-5

Examples II-28 and II-29 and Comparative Example II-6

A negative electrode sheet was produced by using lithium titanateLi₄Ti₅O₁₂ (negative electrode active material) in place of the negativeelectrode active material used in Example II-1 and Comparative ExampleII-1. 80% by mass of lithium titanate Li₄Ti₅O₁₂ and 15% by mass ofacetylene black (electroconductive agent) were mixed and then added toand mixed with a solution which had been prepared by dissolving 5% bymass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone inadvance, thereby preparing a negative electrode mixture paste. Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example II-1 and Comparative Example II-1,except that this negative electrode mixture paste was applied onto onesurface of a copper foil (collector), dried, and treated under pressure,followed by cutting into a predetermined size, thereby producing anegative electrode sheet; and that in evaluating the battery, the finalcharging voltage and the final discharging voltage were set to 2.8 V and1.2 V, respectively; and that the composition of the nonaqueouselectrolyte was changed to a predetermined composition. The results areshown in Table 10.

TABLE 10 Compound represented by formula (I-2) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example II-28 1M LiPF₆ PC/DEC (30/70)

1 87  64 Example II-29

1 82  68 Comparative None — 74 100 Example II-6

All of the lithium secondary batteries of Examples II-1 to II-25 asdescribed above are improved in the storage characteristics at a hightemperature and at a high voltage and inhibited in the gas generationamount, as compared with the lithium secondary batteries of ComparativeExample II-1 which is in the case of not containing the compoundrepresented by the general formula (I-2) and Comparative Example II-2which is in the case of adding the compound described in PTL 4,respectively, the lithium secondary battery of Comparative Example II-3which is in the case of adding the compound described in PTL 5, and thelithium secondary battery of Comparative Example II-4 which is in thecase of adding the compound described in PTL 6.

In the light of the above, it has become clear that the effects broughtin the case of using the energy storage device of the present inventionat a high voltage are peculiar effects brought in the case where thenonaqueous electrolytic solution contains the compound represented bythe general formula (I-2).

In addition, from the comparison of Examples II-26 and II-27 withComparative Example II-5 in the case of using lithium nickel manganate(LiNi_(1/2)Mn_(3/2)O₄) for the positive electrode and also from thecomparison of Examples II-28 and II-29 with Comparative Example II-6 inthe case of using lithium titanate (Li₄TiO₁₂) for the negativeelectrode, the same effects are brought.

In consequence, it is evident that the effects of the present inventionaccording to Embodiment 2 are not an effect relying upon a specifiedpositive electrode or negative electrode.

Furthermore, the nonaqueous electrolytic solution containing thecompound represented by the general formula (I-2) of the presentinvention also has an effect for improving the discharging properties inthe case of using a lithium primary battery at a high voltage.

Synthesis Example III-1 [Synthesis of Dimethyl1,5,2,4-Dioxadithiepane-6,7-dicarboxylate 2,2,4,4-Tetraoxide (SyntheticCompound 3)]

4.19 g (23.5 mmol) of dimethyl tartrate and 5.00 g (23.5 mmol) ofmethanedisulfonyl dichloride were dissolved in 140 mL of ethyl acetateand then cooled to 15° C. To this solution, 4.93 g (48.7 mmol) oftriethylamine was added dropwise at 13 to 17° C. over 10 minutes,followed by stirring at room temperature for 3 hours. The produced saltwas filtered off, the solvent was concentrated under reduced pressure,and the resulting residue was purified by means of silica gel columnchromatography (elution with ethyl acetate/hexane=1/5), therebyobtaining 1.72 g (yield: 23%) of dimethyl1,5,2,4-dioxadithiepane-6,7-dicarboxylate 2,2,4,4-tetraoxide as a whitesolid.

The obtained dimethyl 1,5,2,4-dioxadithiepane-6,7-dicarboxylate2,2,4,4-tetraoxide was subjected to ¹H-NMR and melting pointmeasurement.

The results are shown below.

¹H-NMR (400 MHz, CDCl₃): δ=5.73 (s, 2H), S=5.04 (s, 2H), S=3.90 (s, 6H)

Examples III-1 to III-15 and Comparative Examples III-1 to III-2[Production of Lithium Ion Secondary Battery]

94% by mass of LiCoO₂ and 3% by mass of acetylene black(electroconductive agent) were mixed and then added to and mixed with asolution which had been prepared by dissolving 3% by mass ofpolyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone in advance,thereby preparing a positive electrode mixture paste. This positiveelectrode mixture paste was applied onto one surface of an aluminum foil(collector), dried, and treated under pressure, followed by cutting intoa predetermined size, thereby producing a positive electrode sheet in abelt-like form. A density of the positive electrode except for thecollector was 3.6 g/cm³.

10% by mass of silicon (elemental substance), 80% by mass of artificialgraphite (d₀₀₂=0.335 nm, negative electrode active material), and 5% bymass of acetylene black (electroconductive agent) were mixed and thenadded to and mixed with a solution which had been prepared by dissolving5% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidonein advance, thereby preparing a negative electrode mixture paste. Thisnegative electrode mixture paste was applied onto one surface of acopper foil (collector), dried, and treated under pressure, followed bycutting into a predetermined size, thereby producing a negativeelectrode sheet. A density of the negative electrode except for thecollector was 1.5 g/cm³.

The electrode sheet was analyzed by X-ray diffractometry, and a ratio[I(110)/I(004)] of the peak intensity I(110) of the (110) plane to thepeak intensity I(004) of the (004) plane of the graphite crystal was0.1.

The above-obtained positive electrode sheet, a micro-porouspolyethylene-made film separator and the above-obtained negativeelectrode sheet were laminated in this order, and the nonaqueouselectrolytic solution having each of compositions shown in Tables 11 and12 was added, thereby producing a laminate-type battery.

[Discharge Capacity Retention Rate after High-Temperature ChargedStorage]

<Initial Discharge Capacity>

In a thermostatic chamber at 25° C., the laminate-type battery producedby the aforementioned method was charged up to a final voltage of 4.35 Vwith a constant current of 1 C and under a constant voltage for 3 hoursand then discharged down to a final voltage of 2.75 V with a constantcurrent of 1 C, thereby determining an initial discharge capacity.

<High-Temperature Charged Storage Test>

Subsequently, in a thermostatic chamber at 55° C., this laminate-typebattery was charged up to a final voltage of 4.35 V with a constantcurrent of 1 C and under a constant voltage for 3 hours, and then storedfor 10 days while being kept at 4.35 V. Thereafter, the battery wasplaced in a thermostatic chamber at 25° C., and once discharged under aconstant current of 1 C to a final voltage of 2.75 V.

<Discharge Capacity after High-Temperature Charged Storage>

Further thereafter, the discharge capacity after the high-temperaturecharged storage was determined in the same manner as in the measurementof the initial discharge capacity.

<Discharge Capacity Retention Rate after High-Temperature ChargedStorage>

A discharge capacity retention rate (%) after the high-temperaturecharged storage was determined according to the following equation.

Discharge capacity retention rate (%) after high-temperature chargedstorage=(Discharge capacity after high-temperature chargedstorage)/(Initial discharge capacity)×100

[Evaluation of Gas Generation Amount after High-Temperature ChargedStorage]

A gas generation amount after the high-temperature charged storage wasmeasured by the Archimedean method. As for the gas generation amount, arelative gas generation amount was evaluated on the basis of definingthe gas generation amount of Comparative Example III-1 as 100% c

In addition, the production condition and battery characteristics ofeach of the batteries are shown in Tables 11 to 12.

TABLE 11 Compound represented by formula (I-3) Composition ofelectrolyte Content in salt nonaqueous Discharge Composition ofnonaqueous electrolytic capacity Gas generation electrolytic solutionsolution retention rate amount (volume ratio of solvent) Kind (% bymass) (%) (%) Example III-1      Example III-2      Example III-3  1.2MLiPF₆ EC/DMC/MEC (30/45/25) 1.2M LiPF₆ EC/MEC (30/70) 1.2M LiPF₆EC/VC/DMC/MEC (29/1/45/25)

1        1        0.005 73     71     66 62     64     65 Example III-4 1.2M LiPF₆ 0.1  75 56 EC/VC/DMC/MEC (29/1/45/25) Example III-5  1.2MLiPF₆ 1    81 51 EC/VC/DMC/MEC (29/1/45/25) Example III-6  1.2M LiPF₆3    75 55 EC/VC/DMC/MEC (29/1/45/25) Example III-7  1.2M LiPF₆ 6    6960 EC/VC/DMC/MEC (29/1/45/25) Example III-8  1.2M LiPF₆ EC/VC/DMC/MEC(29/1/45/25)

1    77 53 Example III-9  1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1    83 53 Example III-10 1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1    80 51 Example III-11 1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1    81 53

TABLE 12 Compound represented by formula (I-3) Content in Composition ofelectrolyte salt nonaqueous Discharge Gas Composition of nonaqueouselectrolytic capacity generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example III-8  1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1 77 53 Example III-9  1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1 83 53 Example III-10 1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1 80 51 Example III-11 1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1 81 53 Example III-12     Example III-13     Example III-14 1.2MLiPF₆ + 0.05M LiFOP EC/FEC/VC/DMC/MEC (19/10/1/45/25) 1.2M LiPF₆ + 0.05MLiPO₂F₂ EC/VC/DMC/MEC/GBL (29/1/42/25/3) 1.2M LiPF₆ + 0.05M LESEC/VC/DMC/MEC (29/1/40/25/5)

1     1     1 83     82     85 53     50     49 Example III-15 0.7MLiPF₆ + 0.55M FSI 1 84 46 EC/VC/DMC/MEC (29/1/45/25) Comparative 1.2MLiPF₆ — 54 100  Example III-1 EC/VC/DMC/MEC None (29/1/45/25)Comparative Example III-2 1.2M LiPF₆ EC/VC/DMC/MEC (29/1/45/25)

1 60 85

Example III-16 and Comparative Example III-3

A positive electrode sheet was produced by using LiNi_(1/2)Mn_(3/2)O₄(positive electrode active material) in place of the positive electrodeactive material used in Example III-1 and Comparative Example III-1. 94%by mass of LiNi_(1/2)Mn_(3/2)O₄ coated with amorphous carbon and 3% bymass of acetylene black (electroconductive agent) were mixed and thenadded to and mixed with a solution which had been prepared by dissolving3% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidonein advance, thereby preparing a positive electrode mixture paste. Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example III-1 and Comparative Example III-1,except that this positive electrode mixture paste was applied onto onesurface of an aluminum foil (collector), dried, and treated underpressure, followed by cutting into a predetermined size, therebyproducing a positive electrode sheet; and that in evaluating thebattery, the final charging voltage and the final discharging voltagewere set to 4.9 V and 2.7 V, respectively. The results are shown inTable 13.

TABLE 13 Compound represented by formula (I-3) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example III-16 1.2M LiPF₆ EC/FEC/MEC/DEC (20/10/40/30)

1 77  68 Comparative None — 51 100 Example III-3

Example III-17 and Comparative Example III-4

A negative electrode sheet was produced by using lithium titanateLi₄Ti₅O₁₂ (negative electrode active material) in place of the negativeelectrode active material used in Example III-1 and Comparative ExampleIII-1. 80% by mass of lithium titanate Li₄Ti₅O₁₂ and 15% by mass ofacetylene black (electroconductive agent) were mixed and then added toand mixed with a solution which had been prepared by dissolving 5% bymass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone inadvance, thereby preparing a negative electrode mixture paste. Alaminate-type battery was produced and subjected to battery evaluationin the same manners as in Example III-1 and Comparative Example III-1,except that this negative electrode mixture paste was applied onto onesurface of a copper foil (collector), dried, and treated under pressure,followed by cutting into a predetermined size, thereby producing anegative electrode sheet; and that in evaluating the battery, the finalcharging voltage and the final discharging voltage were set to 2.8 V and1.2 V, respectively; and that the composition of the nonaqueouselectrolytic solution was changed to a predetermined composition. Theresults are shown in Table 14.

TABLE 14 Compound represented by formula (I-3) Content in Composition ofelectrolyte salt nonaqueous Discharge Composition of nonaqueouselectrolytic capacity Gas generation electrolytic solution solutionretention rate amount (volume ratio of solvent) Kind (% by mass) (%) (%)Example III-17 1.15M LiPF₆ PC/DEC (30/70)

1 90  52 Comparative None — 80 100 Example III-4

All of the lithium secondary batteries of Examples III-1 to III-15 asdescribed above are improved in the storage characteristics at a hightemperature and at a high voltage and inhibited in the gas generationamount, as compared with the lithium secondary batteries of ComparativeExample III-1 which is in the case of not containing the compoundrepresented by the general formula (I-3) and Comparative Example III-2which is in the case of adding the compound described in PTL 7,respectively.

In the light of the above, it has become clear that the effects broughtin the case of using the energy storage device of the present inventionat a high voltage are peculiar effects brought in the case where thenonaqueous electrolytic solution contains the compound represented bythe general formula (I-3).

In addition, from the comparison of Example III-16 with ComparativeExample III-3 in the case of using lithium nickel manganate(LiNi_(1/2)Mn_(3/2)O₄) for the positive electrode and also from thecomparison of Example III-17 with Comparative Example III-4 in the caseof using lithium titanate (Li₄Ti₅O₁₂) for the negative electrode, thesame effects are brought.

In consequence, it is evident that the effects of the present inventionaccording to Embodiment 3 are not an effect relying upon a specifiedpositive electrode or negative electrode.

Furthermore, the nonaqueous electrolytic solution containing thecompound represented by the general formula (I-3) of the presentinvention also has an effect for improving the discharging properties inthe case of using a lithium primary battery at a high voltage.

INDUSTRIAL APPLICABILITY

The energy storage device using the nonaqueous electrolytic solution ofthe present invention is useful as an energy storage device, such as alithium secondary battery, etc., having excellent electrochemicalcharacteristics in the case of using a battery at a high temperature andat a high voltage.

1. A nonaqueous electrolytic solution having an electrolyte saltdissolved in a nonaqueous solvent, the nonaqueous electrolytic solutioncomprising from 0.001 to 10% by mass of a carboxylic acid ester compoundrepresented by the following general formula (I):

wherein: each of R¹ and R² independently represents a hydrogen atom, ahalogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkylgroup having 3 to 6 carbon atoms, an alkenyl group having 2 to 6 carbonatoms, an alkynyl group having 3 to 6 carbon atoms, an aralkyl grouphaving 7 to 13 carbon atoms, an aryl group having 6 to 12 carbon atoms,or a —C(═O)—OR⁴ group, and when R¹ and R² are each an alkyl group, thenR¹ and R² may be bonded to each other to form a ring structure; R³represents a hydrogen atom, a halogen atom, or an alkyl group having 1to 6 carbon atoms; n represents an integer of 1 to 3; when n is 1, thenL and R⁴ may be the same as or different from each other and representan alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, analkynyl group having 3 to 6 carbon atoms, an alkoxyalkyl group having 2to 6 carbon atoms, a cyanoalkyl group having 2 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, or an aryl group having 6 to12 carbon atoms, and when n is 2 or 3, then L represents an n-valentconnecting group constituted of a carbon atom and a hydrogen atom, whichmay contain an ether bond, a thioether bond, or an SO₂ bond and R⁴ isthe same as described above; and X is selected from the group consistingof an —S(═O)— group, an —S(═O)₂— group, an —S(═O)₂—R⁵—S(═O)₂— group or aCR⁶R⁷ group, R⁵ represents an alkylene group having 1 to 4 carbon atoms,in which at least one hydrogen atom may be substituted with a halogenatom or an alkyl group having 1 to 4 carbon atoms, and each of R⁶ and R⁷independently represents a hydrogen atom or an alkyl group having 1 to 6carbon atoms, in which at least one hydrogen atom may be substitutedwith a halogen atom, wherein at least one hydrogen atom of the alkylgroup having 1 to 6 carbon atoms, the cycloalkyl group having 3 to 6carbon atoms, the alkenyl group having 2 to 6 carbon atoms, the alkynylgroup having 3 to 6 carbon atoms, the alkoxyalkyl group having 2 to 6carbon atoms, the cyanoalkyl group having 2 to 6 carbon atoms, thearalkyl group having 7 to 13 carbon atoms, or the aryl group having 6 to12 carbon atoms as R¹, R², R⁴, or L, may be substituted with a halogenatom.
 2. (canceled)
 3. (canceled)
 4. The nonaqueous electrolyticsolution according to claim 1, wherein in the general formula (I), X isan —S(═O)— group, an —S(═O)₂— group, or a —CR⁶R⁷ group, and n is
 1. 5.The nonaqueous electrolytic solution according to claim 4, wherein inthe general formula (I), the compound wherein X is an —S(═O)— group, an—S(═O)₂— group, or a —CR⁶R⁷ group is a carboxylic acid ester compoundrepresented by the following general formula (I-2):

wherein: each of R²¹ and R²² independently represents a hydrogen atom, ahalogen atom, an alkyl group having 1 to 6 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, acycloalkyl group having 3 to 6 carbon atoms, an alkenyl group having 2to 6 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR²⁵ group, and when R²¹and R²² are each an alkyl group, then R²¹ and R²² may be bonded to eachother to form a ring structure; R²³ is a hydrogen atom, a halogen atom,or an alkyl group having 1 to 6 carbon atoms; R²⁴ and R²⁵ may be thesame as or different from each other and represent an alkyl group having1 to 6 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, a cycloalkyl group having 3 to 6 carbonatoms, in which at least one hydrogen atom may be substituted with ahalogen atom, an alkenyl group having 2 to 6 carbon atoms, in which atleast one hydrogen atom may be substituted with a halogen atom, analkynyl group having 3 to 6 carbon atoms, an alkoxyalkyl group having 2to 6 carbon atoms, a cyanoalkyl group having 2 to 6 carbon atoms, anaralkyl group having 7 to 13 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, or an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom; and X¹ is an —S(═O) group, an —S(═O)₂group, or a —CR²⁶R²⁷ group and each of R²⁶ and R²⁷ independentlyrepresents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,in which at least one hydrogen atom may be substituted with a halogenatom.
 6. The nonaqueous electrolytic solution according to claim 1,wherein in the general formula (I), X is an —S(═O)₂—R⁵—S(═O)₂— group,and n is 1 or
 2. 7. The nonaqueous electrolytic solution according toclaim 6, wherein in the general formula (I), the compound wherein X isan —S(═O)₂—R⁵—S(═O)₂— group, and n is 1 or 2 is a carboxylic acid estercompound represented by the following general formula (I-3):

wherein: each of R³¹ and R³² independently is a hydrogen atom, a halogenatom, an alkyl group having 1 to 6 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, an aryl grouphaving 6 to 12 carbon atoms, in which at least one hydrogen atom may besubstituted with a halogen atom, or a —C(═O)—OR³⁴ group; R³³ representsa hydrogen atom, a halogen atom, or an alkyl group having 1 to 6 carbonatoms; m represents 1 or 2; when m is 1, then L³ and R³⁴ may be the sameas or different from each other and are selected from the groupconsisting of alkyl group having 1 to 6 carbon atoms, in which at leastone hydrogen atom may be substituted with a halogen atom, a cycloalkylgroup having 3 to 6 carbon atoms, in which at least one hydrogen atommay be substituted with a halogen atom, an alkenyl group having 2 to 6carbon atoms, in which at least one hydrogen atom may be substitutedwith a halogen atom, an alkynyl group having 3 to 6 carbon atoms, analkoxyalkyl group having 2 to 6 carbon atoms, a cyanoalkyl group having2 to 6 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, inwhich at least one hydrogen atom may be substituted with a halogen atom,or an aryl group having 6 to 12 carbon atoms, in which at least onehydrogen atom may be substituted with a halogen atom, and when m is 2,then L³ represents an alkylene group having 2 to 8 carbon atoms, analkenylene group having 4 to 8 carbon atoms, or an alkynylene grouphaving 4 to 8 carbon atoms, and at least one hydrogen atom of L³ may besubstituted with a halogen atom and R³⁴ is the same as described above;and X² is an —S(═O)₂—R³⁵—S(═O)₂— group and R³⁵ represents an alkylenegroup having 1 to 4 carbon atoms, in which at least one hydrogen atommay be substituted with a halogen atom or an alkyl group having 1 to 4carbon atoms.
 8. (canceled) 9: The nonaqueous electrolytic solutionaccording to claim 1, wherein the nonaqueous electrolytic solutionhaving an electrolyte salt dissolved in a nonaqueous solvent comprises0.01 to 5% by mass of the carboxylic acid ester compound represented bythe general formula (I). 10: The nonaqueous electrolytic solutionaccording to claim 1, wherein the nonaqueous electrolytic solutionhaving an electrolyte salt dissolved in a nonaqueous solvent comprisesthe carboxylic acid ester compound represented by the general formula(I) and further comprises LiPF₆ as an electrolyte salt.
 11. An energystorage device comprising a positive electrode, a negative electrode,and a nonaqueous electrolytic solution having an electrolyte saltdissolved in a nonaqueous solvent, the nonaqueous electrolytic solutioncomprising the nonaqueous electrolytic solution according to claim 1.12. The energy storage device according to claim 11, wherein thepositive electrode comprises, as a positive electrode active material, acomplex metal oxide containing lithium and one or more selected fromcobalt, manganese, and nickel, or a lithium-containing olivine-typephosphate. 13: The energy storage device according to claim 11, whereinthe negative electrode comprises, as a negative electrode activematerial, one or more selected from lithium metal, a lithium alloy, acarbon material capable of absorbing and releasing lithium, tin, a tincompound, silicon, a silicon compound, and a lithium titanate compound.14-15. (canceled)
 16. (canceled)
 17. The nonaqueous electrolyticsolution according to claim 5, wherein the carboxylic acid estercompound represented by the formula (I-2) is at least one selected frommethyl 1,3,2-dioxathiolane-4-carboxylate 2-oxide, ethyl1,3,2-dioxathiolane-4-carboxylate 2-oxide, 2-propenyl1,3,2-dioxathiolane-4-carboxylate 2-oxide, 2-propynyl1,3,2-dioxathiolane-4-carboxylate 2-oxide, 2,2,2-trifluoroethyl1,3,2-dioxathiolane-4-carboxylate 2-oxide, methyl5-fluoro1-1,3,2-dioxathiolane-4-carboxylate 2-oxide, dimethyl1,3,2-dioxathiolane-4,5-dicarboxylate 2-oxide, diethyl1,3,2-dioxathiolane-4,5-dicarboxylate 2-oxide, methyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide, ethyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide, 2-propenyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide), 2-propynyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide, 2,2,2-trifluoroethyl1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide, methyl5-fluoro-1,3,2-dioxathiolane-4-carboxylate 2,2-dioxide, dimethyl1,3,2-dioxathiolane-4,5-dicarboxylate 2,2-dioxide, diethyl1,3,2-dioxathiolane-4,5-dicarboxylate 2,2-dioxide, methyl1,3-dioxolane-4-carboxylate, ethyl 1,3-dioxolane-4-carboxylate,2-propenyl 1,3-dioxolane-4-carboxylate, 2-propynyl1,3-dioxolane-4-carboxylate, 2,2,2-trifluoroethyl1,3-dioxolane-4-carboxylate, methyl5-fluoro-1,3-dioxolane-4-carboxylate, dimethyl1,3-dioxolane-4,5-dicarboxylate, diethyl1,3-dioxolane-4,5-dicarboxylate, methyl2,2-dimethyl-1,3-dioxolane-4,5-dicarboxylate and dimethyl2,2-dimethyl-1,3-dioxolane-4,5-dicarboxylate.
 18. The nonaqueouselectrolytic solution according to claim 7, wherein the carboxylic acidester compound represented by the formula (I-3) is at least one selectedfrom methyl 1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide,ethyl 1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide,2-propenyl 1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide,2-propynyl 1,5,2,4-dioxadithiepane-6-carboxylate 2,2,4,4-tetraoxide,2,2,2-trifluoroethyl 1,5,2,4-dioxadithiepane-6-carboxylate2,2,4,4-tetraoxide, methyl1,5,2,4-dioxadithiepane-7-fluoro-6-carboxylate 2,2,4,4-tetraoxide,dimethyl 1,5,2,4-dioxadithiepane-6,7-dicarboxylate 2,2,4,4-tetraoxide,and diethyl 1,5,2,4-dioxadithiepane-6,7-dicarboxylate2,2,4,4-tetraoxide. 19: The nonaqueous electrolytic solution accordingto claim 1, wherein the nonaqueous electrolytic solution furthercomprises at least one selected from lithium salts having an oxalateskeleton, lithium salts having a phosphate skeleton, and lithium saltshaving an S═O group. 20: The nonaqueous electrolytic solution accordingto claim 1, wherein the nonaqueous electrolytic solution furthercomprises at least cyclic carbonate selected from the group consistingof cyclic carbonates comprising a double bond, a triple bond or afluorine atom. 21: The nonaqueous electrolytic solution according toclaim 1, wherein the nonaqueous electrolytic solution further comprisesat least one selected from lithium bis(oxalate)borate (LiBOB), lithiumdifluoro(oxalate)borate (LiDFOB), lithium tetrafluoro(oxalate)phosphate(LiTFOP), lithium difluorobis(oxalate)phosphate (LiDFOP), LiPO2F2,lithium trifluoro((methanesulfonyl)oxy)borate (LiTFMSB), lithium methylsulfate (LMS), lithium ethyl sulfate (LES), lithium 2,2,2-trifluoroethylsulfate (LFES), and FSO3Li. 22: The nonaqueous electrolytic solutionaccording to claim 20, wherein the cyclic carbonate having a fluorineatom is 4-fluoro-1,3-dioxolan-2-one (FEC), or trans- orcis-4,5-difluoro-1,3-dioxolan-2-one (DFEC). 23: A carboxylic acid estercompound represented by the following general formula (III):

wherein: each of R⁵¹ and R⁵² independently represents a hydrogen atom, ahalogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkylgroup having 3 to 6 carbon atoms, an alkenyl group having 2 to 6 carbonatoms, an alkynyl group having 3 to 6 carbon atoms, an aralkyl grouphaving 7 to 13 carbon atoms, an aryl group having 6 to 12 carbon atoms,or a —C(═O)—OR⁵⁴ group, and when R⁵¹ and R⁵² are each an alkyl group,then R⁵¹ and R⁵² may be bonded to each other to form a ring structure;R⁵³ represents a hydrogen atom, a halogen atom, or an alkyl group having1 to 6 carbon atoms; m represents 1 or 2; when m is 1, then L⁵ and R⁵⁴may be the same as or different from each other and represent an alkylgroup having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynylgroup having 3 to 6 carbon atoms, an alkoxyalkyl group having 2 to 6carbon atoms, a cyanoalkyl group having 2 to 6 carbon atoms, an aralkylgroup having 7 to 13 carbon atoms, or an aryl group having 6 to 12carbon atoms, and when m is 2, then L⁵ represents an alkylene grouphaving 2 to 8 carbon atoms, an alkenylene group having 4 to 8 carbonatoms, or an alkynylene group having 4 to 8 carbon atoms, at least onehydrogen atom of L⁵ may be substituted with a halogen atom and R⁵⁴ isthe same as described above; and X³ represents an —S(═O)₂—R⁵⁵—S(═O)₂—group and R⁵⁵ represents an alkylene group having 1 to 4 carbon atoms,in which at least one hydrogen atom may be substituted with a halogenatom or an alkyl group having 1 to 4 carbon atoms, wherein at least onehydrogen atom of the alkyl group having 1 to 6 carbon atoms, thecycloalkyl group having 3 to 6 carbon atoms, the alkenyl group having 2to 6 carbon atoms, the alkynyl group having 3 to 6 carbon atoms, thealkoxyalkyl group having 2 to 6 carbon atoms, the cyanoalkyl grouphaving 2 to 6 carbon atoms, the aralkyl group having 7 to 13 carbonatoms, or the aryl group having 6 to 12 carbon atoms as R⁵¹, R⁵², R⁵⁴,or L⁵, may be substituted with a halogen atom.